Recast with Kremlin's comments.
Russian authorities on Monday accused Kyiv of attacking the Crimea bridge, killing two people and damaging part of the roadway that connects the Moscow-annexed peninsula with southern Russia's Krasnodar region.
"We know the reasons and those who are behind this terrorist act. This will require further concentration from all of us and additional measures and work," Kremlin spokesperson Dmitry Peskov said.
Just hours earlier, Russia’s Investigative Committee, which probes serious crimes, launched a criminal investigation into what it called a “terrorist attack” that was orchestrated by “Ukrainian special services.”
The Investigative Committee also confirmed that a husband and wife had been killed in the attack, while their daughter was hospitalized with injuries.
President Vladimir Putin denounced what he called a “terror attack” and called for tougher security measures following the bridge attack.
"Another terrorist attack was committed on the bridge last night," Putin said in televised remarks. “I am waiting for specific proposals to improve the security of this strategic, important transport facility.”
Pro-war military bloggers and Russian media reported that two explosions hit the bridge early Monday, but these reports could not immediately be confirmed.
Deputy Prime Minister Marat Khusnullin, who oversaw the restoration of the Crimea bridge after it was attacked in October, said Monday that rail traffic along the bridge continued as usual and that inspections of the latest damage were underway to determine how quickly repairs could be made.
Meanwhile, sources told AFP that the Ukrainian navy and its SBU security service carried out an attack on the Crimea bridge.
"Today's attack on the Crimean bridge is a special operation of the SBU and the navy," the security service source said. The strike was carried out using waterborne drones, according to the same source.
Crimea has been regularly hit by strikes and attacks targeting Russian-installed officials and infrastructure over recent months that Moscow has blamed on Kyiv.
AFP contributed reporting.