Fighting has raged in Ukraine since Russia launched a full-scale invasion more than three years ago.

Russian forces have slowly expanded the amount of territory they control over the past year, mostly in the east of Ukraine.

The Russian Federal Security Service (FSB) say they have detained a Ukrainian special services agent in a statement released this afternoon.

The FSB said the individual had been detained "for the manufacture of an improvised explosive device (IED) to commit sabotage and terrorist acts on the peninsula" although it does not specifically mention the bridge.

According to the statement, the individual put the IED in an area in the Balaklava district of Sevastopol - located on the other side of Crimea from the Kerch Bridge.

It also claims that he received instructions from the Ukrainian security service via a video link.

The FSB's investigation department has started a criminal case.

The Kerch Bridge has reopened, according to the official Telegram channel that shares operational updates about the bridge.

In an update posted at 17:42 local time (15:42 BST), the says: "Traffic on the Crimean Bridge has been resumed."

In a further update some 20 minutes later, it adds there are approximately 400 cars waiting to cross the bridge towards either Taman - the first Russian village across the Kerch Strait - or Kerch in Crimea.

At the moment we don't have confirmation if the multi-lane bridge has fully reopened, or if there are restrictions to traffic.

Image source, Getty Images

In the Turkish city of Istanbul on Monday a second round of peace talks between Ukraine and Russia ended with no major breakthrough.

However, both sides did commit to exchanging more prisoners of war, after hundreds of soldiers were swapped last month.

A key demand by Ukraine and its European allies was an "unconditional ceasefire" but Kyiv's negotiators said Russia had rejected this again.

The Russian side said its team had suggested a front-line truce lasting two or three days "in certain areas".

In the end, yesterday's talks resulted in the two countries committing to returning the bodies of 12,000 soldiers. They also agreed to exchange all sick and heavily wounded prisoners of war, as well those aged under 25.

Expectations were low even before the talks started.

Both sides remain deeply divided on how to end the war and there were reports of attacks on both sides in the hours before the discussions got under way.

The attack on the Kerch Bridge follows other bridge incidents in Russia in the past few days, which Ukraine has said were "false flag" operations.

Two bridges collapsed on Saturday night in border regions in Russia - killing at least seven people and injuring dozens more.

A road bridge came down in Bryansk, bringing several heavy trucks onto a moving enger train late on Saturday, the regional governor said. Hours later another bridge collapsed in the Zheleznogorsk district of Kursk, derailing a locomotive train.

Russian media said these were being investigated as terrorism acts. The Kremlin said President Putin had been informed of the incidents.

But a Ukrainian national security official said the incidents were Russian "false flag" operations, designed to "manipulate international opinion" ahead of peace talks that took place on Monday.

Image source, Telegram / Alexander Khinshtei

The US has sent explosives to Ukraine - though there's no evidence they were used herepublished at 15:34 British Summer Time 3 June

15:34 BST 3 June

Chris Partridge
BBC weapons analyst

Image source, Ukraine's SBU

Ukraine’s Security Service, the SBU, talks about 1,100kg of the equivalent of TNT being used against the bridge.

What’s worth noting is that the United States has repeatedly sent C-4 explosive to Ukraine, as part of its military aid programme, over the past three years.

C-4 is a plastic explosive that can be moulded into any desired shape. It is characteristically stable, largely unaffected by physical shocks and can only be set off with a detonator.

We don’t know how much C-4 has been sent to Ukraine, but this is what the US State Department said in March, external, when detailing what had been sent to Ukraine: "C-4 explosives, demolition munitions, and demolition equipment for obstacle clearing."

That description would fit the type of attack carried out here, although it’s important to note there is no confirmation - or direct evidence - that C-4 was actually used.

Paul Brown
BBC senior journalist

Image source, Ukraine SBU/PLANET

We're currently investigating reports of one or two incidents at the Kerch Bridge that connects Russian-occupied Crimea with Russia.

Ukraine's security service, the SBU, said in a social media post “agents mined the s of this illegal facility. And today, without any civilian casualties, at 4:44 am the first explosive device was activated!"

The post was accompanied by a video showing an explosion near one of the bridge s and a still image showing damage to railings above.

The image and video both appear to be taken from CCTV footage, with the latter bearing a timestamp for today at 06:22 local time.

The footage allowed us to geolocate the explosion to the eastern edge of the road bridge beneath an arched section.

According to one state-run Russian news agency the bridge was closed for three hours this morning.

We cannot yet the SBU's claim that it used 1.1 tonnes of explosives and the bridge was left "in a state of emergency".

We are now looking into reports of another incident at the bridge which forced it to close again.

The 10-mile Kerch Bridge was inaugurated in 2018, four years after Russia's annexation of the peninsula. It is considered a legitimate military target by Ukraine.

Laura Gozzi
Europe reporter

As is often the case when these attacks occur, piecing together the latest details can be difficult.

If the operation is still under way, the side carrying out the attack may want to keep quiet - while the target doesn't want to attract attention and look weak.

At this stage, this is what we do know:

• Video emerges: Around three hours ago, Ukraine's Security Service put out a video purporting to show an attack carried out hours before, in which they said underwater explosives detonated near the pillars of the Kerch Bridge, which links Russia with Crimea
• Bridge closes: Russia did not comment, but in the early hours of Tuesday, the bridge was closed for a few hours - then reopened to traffic at about 10:00 (07:00 GMT)
• Reports of further attacks: Soon after the SBU put out its statement, reports of another explosion began to emerge
• Bridge shuts again: Those haven't been confirmed by either Russia or Ukraine - but at about 16:00 local time (13:00 GMT / 14:00 BST) the bridge was closed again
• 'Remain calm': The official Telegram channel that shares operational updates about the bridge says: "We ask those on the bridge and in the inspection zone to remain calm and follow the instructions of the transport security officers"

Paul Adams
Diplomatic correspondent, reporting from Kyiv

Ukraine's security service, the SBU, says the attack on the Kerch Bridge has been planned for months.

It says its agents planted the equivalent of over a thousand kilogrammes of TNT underwater to damage the bridge’s foundations.

Video footage from early this morning appears to show the moment of detonation. The SBU said it left the vital bridge in what it called an emergency condition.

Traffic was halted for a few hours, with the bridge re-opening soon afterwards. But this afternoon, it appears to have closed again, following a second reported explosion.

The Kerch Bridge was opened by President Putin, amid great fanfare, in 2018, following his annexation of Crimea four years earlier.

Ukrainians, who still claim the peninsula as their own sovereign territory, have long regarded it as illegal.

When the SBU exploded a truck bomb on the bridge in 2022, the operation was greeted with euphoria across Ukraine.

This morning's claimed attack by Ukraine on the Kerch Bridge in Crimea follows a major attack by Ukraine across Russia over the weekend.

On Sunday, Ukraine executed an operation known as "Spider's Web", using more than 100 smuggled drones to attack Russian bomber planes at remote airfields deep in the country.

Ukraine said it was its biggest long-range attack of the war, with President Zelensky claiming they had hit a third of Russia's strategic cruise missile carriers.

SBU sources told BBC News it took a year and a half to organise the strikes.

The bridge that was seemingly hit by Ukraine's underwater explosives was built by Russia after it invaded and annexed the Crimean Peninsula in 2014.

Known as the Kerch Bridge, it was inaugurated by President Vladimir Putin to great fanfare in 2018.

In Ukraine, the bridge - which has separate sections for road and rail traffic - is a hated symbol of Russian occupation. It is used by Russia to supply its military in occupied parts of Ukraine.

Ukraine's security service (SBU) has released a video which purports to show the moment an explosion damaged the bridge.

It was released alongside a statement describing the operation, which says explosives detonated by SBU agents damaged the bridge's underwater s.

The explosion happened in the early hours, it says.

Ukraine's security service says it has hit a strategic road and rail bridge linking Russia to occupied Crimea below the water level with explosives.

It says 1,100kg of explosives had been placed deep under water over the course of several months and detonated remotely before 05:00 local time this morning.

It claims the bridge's underwater pillars have been damaged.

Traffic across the Kerch Strait was initially suspended and then resumed. But local authorities have since warned the bridge has closed again.

The bridge - also known as Kerch Bridge - was built by Russia after it invaded and annexed the Crimean Peninsula in 2014.

A key supply route for Russian forces in Ukraine, the bridge has already been hit twice since the start of the war in 2022.

Image source, Ukraine SBU