Russia ramped up security on its only bridge

President Vladimir Putin has now ordered the country's Federal Security Service (FSB) to oversee the key connector to the occupied peninsula.

The bridge is also a pivotal symbol of Russia's annexation of Crimea from Ukraine in 2014. The blast killed three people, Russian investigators said.

Officials said work to fix the damaged sections would begin immediately.

Russia's deputy prime minister ordered the destroyed parts of the bridge to be taken down immediately, and said divers would begin investigating damage below the waterline on Sunday morning, Russian news agencies report.