Russia's Defence Ministry has said it had hit military targets in two Ukrainian port cities overnight as "a mass revenge strike" in response to an attack on the Crimean bridge the previous day which it blamed on Kyiv.
The ministry said it had struck Odesa, where the Ukrainian navy has its headquarters, and Mykolaiv, near Ukraine's Black Sea coast.
The attack came just hours after Moscow refused to extend a deal allowing the safe export of grain from the region.
"The armed forces of the Russian Federation carried out a mass retaliatory strike overnight using precision sea-based weapons against facilities where terrorist acts against the Russian Federation were being prepared using uncrewed boats," the ministry said in a statement.
It said it had struck a ship repair plant near Odesa where such boats - thought to be naval drones of the kind Russia believes were used to attack the Crimean bridge - were being built.
"In addition, storage facilities holding around 70,000 tons of fuel used to supply the Ukrainian military's equipment were destroyed" near the cities of Mykolaiv and Odesa, it said.
It said all the targets had been struck and destroyed, citing fires and detonations as evidence. Reuters could not independently confirm the account.
Ukraine's air force said earlier that six cruise missiles and 31 out of 36 drones had been shot down, mostly over the coastal Odesa and Mykolaiv regions in the south.
A Russian couple was killed and their 14-year-old daughter wounded yesterday in what Moscow said was a Ukrainian attack that knocked out the road part of the bridge linking Russia to Crimea, which Moscow annexed from Ukraine in 2014.
Kyiv has not claimed responsibility for the attack.
Read more: Crimea bridge: Why is it important and what happened to it?
Ukrainian media said Ukrainian security services had used naval drones to attack the bridge, which had only recently returned to full operation after suffering severe damage in a similar attack last October.
Kremlin spokesman Dmitry Peskov said today it had been clear to Moscow from the start that Ukraine was behind the attack, which prompted some Russian tourists to flee Crimea by driving through parts of southern Ukraine controlled by Russian forces.
Mr Peskov confirmed that the overnight strikes had been revenge for the bridge attack.
Meanwhile, Russia's defence ministry and local officials say they shot down 28 Ukrainian drones over Crimea overnight.
Seventeen drones sent by Ukraine's forces overnight were "destroyed" and another 11 were "suppressed" by electronic means, Russia's defence ministry said in a statement.
It said there were no casualties or damage.
Drone attacks in Crimea have increased in recent weeks as Ukraine wages a counter-offensive against Russian forces.
Russia annexed Crimea from Ukraine in 2014, a move not recognised by the international community.
Kyiv has repeatedly said it plans to take back the peninsula.
Waterborne drones struck the sole bridge connecting Russia to Crimea yesterday. The explosion hit the Kerch bridge, a major conduit for Russia's troops in Ukraine, just hours before a crucial deal to export Ukrainian grain was to expire.
The bridge has partially reopened to traffic on one lane since the attack.
"Motor transport on the Crimean Bridge has been restored in reverse mode on the most outer right lane," Russian Deputy Prime Minister Marat Khusnullin said.
However, ferry operations were suspended early due to bad weather, Russian agencies reported, citing the Moscow-backed emergency situations ministry of Crimea.
