An explosion tore through Russia’s bridge across the Kerch Strait to Crimea early on Saturday, severely damaging it in a major blow to Vladimir Putin more than seven months into his invasion of Ukraine.

Russia’s anti-terrorist committee said a truck exploded on the bridge’s roadside in the early hours of Saturday morning and caused seven fuel tanks on the railway bridge which runs alongside it to ignite.

Putin, Russia’s president, ordered senior officials and security agencies to investigate the explosion, which sent huge clouds of smoke into the sky as a blaze raged, causing two road spans of the bridge to collapse and scorching part of the railroad.

The apparent attack is another humiliation for Russia as its invasion of Ukraine, originally designed to capture Kyiv in a matter of days, continues to struggle.

The bridge is a major conduit to supply Russia’s war effort in south-eastern Ukraine, where its troops have made substantial retreats in the last week from territory Putin claimed as Russian after annexing four Ukrainian regions.

Putin had attempted to raise the stakes in Ukraine following a series of battlefield setbacks by claiming the territories as Russian soil — allowing him to reframe the invasion as a defensive war, justifying the mobilization of the army’s reserves, and raising the threat Russia could use nuclear weapons if Ukraine tried to take the regions back.

Instead, the quagmire has only deepened. Many Russian people have fled to Kazakhstan to avoid military service, while Ukraine continues to make advances in the east and south, prompting rare public criticism of the army from some officials and on state television.

The 12-mile bridge was devised when Russia annexed Crimea from Ukraine in 2014 and completed in 2018. It is an engineering feat — the Wehrmacht and

Red Army both tried and failed to cross the waters linking the peninsula to the Russian mainland in the second world war — and has become a symbol of Russian prestige.

Putin opened the bridge in 2018 when he drove a truck across it alongside his childhood judo sparring partner Arkady Rotenberg, the billionaire he placed in charge of building it.