Odesa, Ukraine - A Russian overnight strike damaged port infrastructure facilities in southern Ukraine's Odesa, Kyiv's military said on Tuesday, hours after Moscow refused to extend a deal allowing the safe export of grain from the region.

Six Kalibr missiles launched towards Odesa and 21 Iran-built attack drones approaching the region were "destroyed" by air defenses, Ukraine's military southern command said in a statement.

"Unfortunately, the debris of the downed missiles and the blast wave from the downing damaged the port infrastructure facilities and several private homes," the southern command said.

Ukraine's air force said a total of 31 drones were downed across the country out of 36 launched by Russia overnight.

Viral Video of the Day Viral Video of the Day for April 28, 2024: Dog gives the biggest smile at exciting pet resort!

Moscow said Tuesday it had carried out a "retaliation strike" against sites that it claimed were involved in planning an attack on the bridge to Crimea.

"At night, the Armed Forces of the Russian Federation delivered a group retaliation strike with high-precision sea-based weapons at facilities where terrorist acts against Russia had been prepared using unmanned boats," the Russian army said in a statement.

The Odesa region is home to maritime terminals that were key to the grain export agreement between Moscow and Kyiv that enabled the shipment of more than 32 million tonnes of Ukrainian grain in the past year.

An "industrial facility" in the southern port city of Mykolaiv was also hit in the overnight attack according to local governor Vitaliy Kim.

A fire had subsequently broken out before being extinguished, he said on Telegram, adding there were no casualties.

Moscow's invasion last year saw Ukraine's Black Sea ports blocked by warships until the agreement, brokered by the UN and Turkey and signed in July 2022, allowed for the passage of critical grain shipments.

Russia refused to extend the deal on Monday, sparking outrage from the United Nations, which warned millions of the world's poorest would "pay the price".

The Kremlin said it was exiting the deal, after months of complaining that elements allowing the export of Russian food and fertilizers had not been honored.

Joke of the Day Joke of the Night for April 26, 2024: The best jokes to laugh the day away

UN Secretary General António Guterres said Moscow's move would "strike a blow to people in need everywhere."

"Hundreds of millions of people face hunger and consumers are confronting a global cost-of-living crisis. They will pay the price," he told reporters.

Ukrainian President Volodymyr Zelensky said Ukraine was prepared to keep exporting grain via the Black Sea despite Russia's exit.

"We are not afraid. We have been approached by companies that own ships. They said that they are ready" to continue shipments, Zelensky said.

Moscow's withdrawal could see Russian ships once again prevent grain exports by blockading Ukrainian ports, as they did during the first months of the war in a move that helped drive up global food prices.

The UN said a final ship carrying Ukrainian grain through the Black Sea was inspected in Istanbul on Monday, a few hours before the deal expired.

Moscow's withdrawal from the deal came hours after drones struck the only bridge connecting Russia's mainland to the annexed Crimea peninsula, a key supply line for Russian forces in the south of Ukraine.

Kyiv's navy and SBU security service carried out the "special operation" using seaborne drones, a security service source told AFP.

Russian authorities said a civilian couple was killed and their daughter wounded in the attack on the Kerch bridge, which was also damaged last year in a blast Moscow blamed on Kyiv.

Russian President Vladimir Putin condemned a "senseless crime" in televised remarks, vowing a "response" and calling for tighter security at the bridge.

Local officials said traffic across the bridge had been halted and encouraged holidaymakers stranded in Crimea to drive home through occupied Ukraine.

Vehicle traffic was later "restored in reverse mode on the far right lane" of the bridge, Russian Deputy Prime Minister Marat Khusnullin said.