Russian President Vladimir Putin said on Sunday that the explosion on the Crimean Bridge on Saturday was an "act of terrorism," according to a statement from the Kremlin.
Putin accused Ukraine of orchestrating the explosion, saying during a meeting with Alexander Bastrykin, chairman of the Investigative Committee of Russia, that Ukraine's special services were the "initiators, performers and masterminds."
"It was a terrorist act aimed at destroying critical civilian infrastructure of the Russian Federation," Putin said.
Bastrykin said Federal Security Service field agents helped to identify suspects, including those active within the Russian Federation. He added that Ukraine's special services and citizens of Russia and foreign countries assisted in the attack.
Ukraine has not commented on the claim.
A deadly blast on Saturday hit the 19-kilometer Crimean Bridge, which consists of two parallel routes for automobiles and trains over the Kerch Strait.
According to Russia, a truck exploded on the road bridge, causing seven fuel tanks of a train heading to the Crimean Peninsula to catch fire. Three people were killed in the blast, which also led to the partial collapse of two spans of the road bridge.
The All-Russian Union of Insurers estimated the damage of the blast at 200-500 million rubles (about $3-8 million), RIA reported.
Traffic has reopened to cars and buses with a full inspection procedure needed, while trucks are still required to cross the Kerch Strait by ferry, Crimea's head Sergei Aksyonov said.