Views are growing that battles in the Black Sea could intensify as Russia has continued to attack the southern Ukrainian port city of Odesa. Moscow has also warned that it will consider any ships bound for Ukraine as potential carriers of military cargo.

Authorities in Odesa said on Thursday that Russian forces attacked the city center, causing a fire. Local media reported that a missile attack damaged buildings and injured at least four people.

Russia has been carrying out missile and drone attacks daily on Odesa and its suburbs, where grain shipment facilities are located, since it announced on Monday that it had pulled out of a deal that allowed Ukrainian grain exports from Black Sea ports. Odesa is one of them.

A US think tank, the Institute for the Study of War, said on Wednesday that the extensive attack is likely intended "to further emphasize Russia's objections to the renewal of the Black Sea grain deal and hinder Ukraine's ability to export grain."

Moscow's warning on vessels approaching Ukraine through the Black Sea also came on Wednesday.

Britain's defense ministry said on Thursday that the Russian Black Sea Fleet "will likely now take a more active role in disrupting any trade which continues."

The ministry went on to caution that the Russian fleet's "blockade operations will be at risk from Ukrainian uncrewed surface vehicles and coastal defence cruise missiles."