The overnight collapse of two bridges in Russian regions bordering Ukraine that killed seven people were caused by explosions, Russian officials said on Sunday, treating them as “acts of terrorism”.

In Russia’s Bryansk region, an explosion caused a road bridge to collapse onto a railway line late Saturday, derailing a passenger train heading to Moscow and killing seven people, authorities said.

A separate rail bridge in the neighbouring Kursk region was blown up hours later in the early hours of Sunday, derailing a freight train and injuring the driver.

Authorities did not say who was behind the explosions, but investigators said a criminal inquiry was underway.

Russian President Vladimir Putin was briefed on the incidents throughout the night, the Kremlin said.

Videos posted on social media from the Bryansk region showed rescuers clambering over the mangled chassis of a train belonging to national operator Russian Railways, while screams could be heard in another video.

“There are seven dead as a result of the collapse of a bridge onto railway tracks,” Alexander Bogomaz, the Bryansk region’s governor, wrote on Telegram. At least 71 people were injured, 44 of whom were in hospital, he told reporters.

“Last night… in the Zheleznogorsk district, a bridge collapsed while a freight locomotive was passing. Part of the train fell onto the road below the bridge,” Kursk region governor Alexander Khinshtein said on Telegram.

“One of the locomotive drivers suffered leg injuries, and the entire crew was taken to hospital,” he said.

‘Illegal interference’

There was no immediate comment from Russian investigators as to who was behind the blasts.

A spokeswoman for Russia’s Investigative Committee said the incidents had been “classified as acts of terrorism”, without elaborating.

But senior ruling party lawmaker Andrey Klishas blamed Ukraine, describing it as a “terrorist enclave”.

Russia has been hit by dozens of sabotage attacks since Moscow launched its full-scale military assault on its neighbour in 2022, many targeting its vast railroad network.

Kyiv says Russia uses railroads to transport troops and weaponry to its forces fighting in Ukraine.

An AFP reporter saw relatives waiting for loved ones to arrive from the Bryansk region at a station in central Moscow.

“Russian Railways said that those who had survived would be coming here,” said 30-year-old entrepreneur Sergey Trinkinets. “My dad finally got in touch. He said he had some bruises and wasn’t feeling very well, so I came to meet him.”

In one video posted on social media, purportedly taken at the scene of the incident in the Bryansk region, someone could be heard screaming as eyewitnesses rushed to find help.

“How did the bridge collapse? There are children there!” a woman can be heard shouting in the video.

Russia’s emergency ministry said a team was on site in the Bryansk region, while Russian Railways said it had dispatched repair trains to the scene.

The incidents came on the eve of a possible meeting between Russian and Ukrainian officials in Istanbul, amid a US-led diplomatic push to end the three-year-long conflict.

Moscow’s three-year assault on Ukraine has resulted in tens of thousands of deaths. Russia currently occupies around a fifth of its neighbour.