A bridge connecting Crimea to Russia was hit by a "truck bombing," Russian authorities said Saturday.
A fire broke out early Saturday morning on the Kerch Bridge -- preceded by an explosion -- causing suspension of traffic and bringing bus and train services to a halt.
The Kerch Bridge -- a pair of parallel bridges, one road and one railroad -- is a key supply route for Russia which was built after Crimea's annexation in 2014.
Footage and images, widely shared on social media, show that a road section collapsed and train carriages were burning on the bridge, which is the longest in Europe.
According to the Russian Anti-Terrorism Committee, the bridge was damaged by "a truck bombing."
Train services to Crimea were temporarily suspended in the aftermath of the explosion and ticket sales were paused, according to the Russian Railways.
Authorities also cancelled bus trips from Crimea.
Russian President Vladimir Putin has ordered the formation of a state commission to investigate the incident, official news agency TASS cited Kremlin Spokesman Dmitry Peskov as saying.
The fire was extinguished later in the day, Russian authorities said, confirming no casualties were reported.
Thousands of tourists remain stranded in Crimea after the explosion, multiple tour groups said.
'Just the beginning'
Although Ukraine did not directly claim responsibility for the attack, multiple statements by top Ukrainian officials pointed to the possibility.
Crimea is Ukraine, Ukraine's Foreign Ministry said on Twitter.
Ukraine's senior presidential adviser Mykhailo Podolyak said what happened on the bridge is just "the beginning."
"Everything illegal must be destroyed, everything stolen must be returned to Ukraine, everything occupied by Russia must be expelled," Podolyak said in a tweet.
Ukraine's National Security and Defense Council Secretary Oleksiy Danilov shared a video split in two parts, with one side displaying the fire on the bridge and the other side playing Marilyn Monroe's famous "Happy Birthday Mr. President" song.
"Putin should be happy. Not everyone gets such an expensive present on their birthday," a Ukrainian official told the New York Times speaking on the condition of anonymity.
On Friday, the Russian president turned 70.
Russia condemned the remarks by Ukrainian officials.
The reaction of the Kyiv regime to the destruction of civilian infrastructure testifies to its terrorist nature," Russian Foreign Ministry spokeswoman Maria Zakharova said on Telegram.
Russia's Energy Ministry said Crimea was supplied with at least 15 days of fuel.
Also, Crimea has two-month supplies of essential goods, authorities said.
Russia's Transport Ministry said they are assessing the damage caused on the bridge.
Russia launched a war in Ukraine on Feb. 24, which has left 6,114 people dead and 9,132 injured, according to UN estimates.
The war has pushed the world in two camps with Western nations imposing crippling economic sanctions on Russia, and Moscow retaliating by threatening of gas supply cuts to Europe.