Ukraine says it struck the road and rail bridge linking Russia and Crimea with underwater explosives.
A video of the explosion on Kerch Bridge was posted on Ukraine's security service (SBU) X account.
The planned attack took "several months" of work and involved detonating 1,100kg of explosives overnight, which "severely damaged" the foundations of the bridge, according to the SBU.
Russia is yet to respond but authorities say bridge crossings have restarted after it was closed for most of the day on Tuesday.
Vladimir Putin opened the 12-mile bridge in 2018. It holds symbolic and strategic significance for Russia, which uses it to transport supplies and weapons to its forces in occupied Crimea.
It is the third time Ukraine has hit the structure after attacks in 2022 and 2023.
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