Russia has issued a veiled warning against any ships bound for Ukraine ports, declaring that all vessels would be deemed as “potential carriers of military cargo”.

Russia’s Defence Ministry issued a statement on Thursday (AEST) saying the move would come into effect within hours.

However, Russia did not explicitly state that it might attack the ships.

Any vessels travelling on Black Sea waters would also be considered party to the conflict on Ukraine’s side.

The warning comes after Russia launched “hellish” overnight strikes on two of Ukraine’s Black Sea ports, which Ukraine said appeared to be deliberately targeting grain export infrastructure.

Russia launched a massive air attack on the Ukrainian port of Odessa for a second consecutive night.

“It was a hellish night,” Odessa military administration spokesman Serhiy Bratchuk said on his Telegram channel.

Grains terminals were damaged, as well as an industrial facility, warehouses, shopping malls, residential and administrative buildings and cars.

An attack in Odessa appeared to target grain export infrastructure, says Ukraine. Photo: Ukraine State Emergency Services

Flames and smoke rose from shattered warehouses in video released by the emergencies ministry, which also showed a residential block with shattered windows.

“Russian terrorists absolutely deliberately targeted the infrastructure of the grain deal,” Ukrainian President Volodymyr Zelensky said on the Telegram messaging app.

“Every Russian missile – is a strike not only on Ukraine but on everyone in the world who wants normal and safe life.”

The attacks on one of Ukraine’s main ports for exporting grain followed a pledge of retaliation by Russia after a blast on a bridge linking Russia to the Crimean Peninsula on Monday that Moscow blamed on Ukraine.

Shortly after the bridge was hit, Moscow withdrew from the Black Sea grain agreement that allowed for the safe export of Ukraine’s grain.

The United Nations said ending the agreement risked creating hunger around the world.

Ukraine said it was setting up a temporary shipping route to Romania.

There was no immediate response from Russia, which said on Tuesday it had hit military targets in two Ukrainian port cities overnight as “a mass revenge strike” for a blast that damaged its bridge to Crimea, which it seized from Ukraine in 2014.

Ukraine’s air force said on Wednesday 63 missiles and drones had been launched across the country by Russia, mainly focused on infrastructure and military facilities in the Odesa region.

Air defences had shot down 37 of them, it said, a lower proportion than it has usually reported over months of attacks.

A considerable part of the grain export infrastructure at Chornomorsk port south west of Odessa was damaged, agriculture minister Mykola Solsky said, adding that 60,000 tons of grain had been destroyed.

The Odessa region’s three ports have been the only ones operating in Ukraine during the war under the UN-brokered Black Sea Grain Initiative – designed to allow Ukrainian grain exports that are vital to global supplies through a Russian blockade of Ukraine’s ports.