Light traffic has resumed on Russia's only bridge to Crimea, hours after a huge blast brought down sections of the roadway.

The blast on Europe's longest bridge - a symbol of Russia's annexation of the peninsula from Ukraine in 2014 - killed three people, investigators say.

The victims were in a nearby car when a lorry blew up, Russian officials claim.

The railway part of the bridge - where oil tankers caught fire - has also apparently reopened.

On Saturday evening, Russia's foreign ministry published a video, seemingly showing cars using the bridge.

he rail and road crossing was opened in 2018 and is a key supply route for Russia's invasion of Ukraine.

An adviser to Ukraine's President Volodymyr Zelensky, Mykhailo Podolyak, did not directly claim Ukrainian responsibility but wrote: "Crimea, the bridge, the beginning.

"Everything illegal must be destroyed, everything stolen must be returned to Ukraine, everything occupied by Russia must be expelled."

Ukraine's defence ministry compared the bridge explosion to the sinking of Russia's Moskva missile cruiser in April.

"Two notorious symbols of Russian power in Ukrainian Crimea have gone down," it tweeted. "What's next in line?"

The Ukrainian government itself simply tweeted: "Sick burn."

Russia's foreign ministry said: "The Kiev [Kyiv] regime's reaction towards destruction of civilian infrastructure is a testament to its terrorist nature."

In other developments:

Ukraine's giant Zaporizhzhia nuclear plant, which is held by Russian forces, has lost all external power and is relying on emergency diesel generators for the electricity it needs for reactor cooling, according to the director general of the UN nuclear watchdogRussia has appointed Air Force General Sergey Surovikin as the new commander to lead its forces in UkraineRussian media accused Ukrainian forces of shelling a printing house in the separatist-held city of Donetsk. 

It is hard to exaggerate the significance, and symbolism, of seeing the bridge - which was opened by President Putin - on fire.

Russia has used the bridge to move military equipment, ammunition, and personnel from Russia to battlefields in southern Ukraine. 

As such, Ukrainian authorities said it was a legitimate target, as they vow to retake the peninsula.

Any attack on Crimea, where the Russian army has a massive presence, will be seen as another massive humiliation for the Kremlin. 

The bridge is particularly hated by Ukrainians. Social media in Ukraine erupted in celebration on seeing the fire - one day after Russian President Vladimir Putin turned 70. 

Local authorities in Crimea organised a ferry service between the Russian mainland and the peninsula, for heavier vehicles that can't use the partially reopened bridge.