An explosion on Sunday rocked a bridge linking Russia-occupied Crimea with Russia and brought down large sections of the bridge.?

Russia occupied Ukraine's Crimea in 2014 and annexed it, just like the four regions it annexed recently.?

Russian authorities said that a truck bomb caused a fire and the collapse of a section of Kerch Bridge. Visuals on the social media show the bridge enveloped in a ranging fireball and sections of a road running alongside it broken.

The bridge is a key supply artery for Russian war effort in southern Ukraine. If the bridge is made inoperable, then it would be a major blow for Russia.

The BBC notes that it's the only crossing between Russia and Crimea.

"A blast on the road section led to oil tankers on the rail section catching fire, before the road collapsed...It is said to be a key target for Ukrainian forces who have been attacking Russian logistics," reported BBC, adding that experts say it's not believed to be caused by a missile.?

The attack on the bridge comes a day after Russian President Vladimir Putin turned 70, dealing him a humiliating blow that could lead him to up the ante in his war on Ukraine.

Russia's National Anti-Terrorism Committee said that the truck bomb caused seven railway cars carrying fuel to catch fire, resulting in a "partial collapse of two sections of the bridge". The committee didn't immediately apportion blame.

The Crimean Peninsula holds symbolic value for Russia and is key to sustaining its military operations in the south. While Russia seized the areas north of Crimea early during the invasion and built a land corridor to it along the Sea of Azov, Ukraine is pressing a counteroffensive to reclaim them.

Reacting to the blast, explosives expert Mick Ryan said on Twitter that it would require at least a "few trucks" of explosives to bring down sections of such a strong bridge.

"The Ukrainians so far have been excellent at operational design and shaping operations in advance of their advances. This could be part of their design for taking back Crimea in the short term — or part of a deception operation to distract from other areas...This is a massive influence operation win for Ukraine. Even if they didn’t do it, it is a demonstration to Russians, and the rest of the world, that Russia’s military cannot protect any of the provinces it recently annexed," said Ryan, an Adjunct Fellow at think tank Center for Strategic and International Studies (CSIS).

(With PTI inputs)