A dozen oil-product tankers, a sunflower oil carrier, and 45 bulkers used to transport grains, ore and coal have gotten stuck, according to ship-tracking data compiled by Bloomberg. There are also fifty-four cargo carriers and a container vessel that sailed into Odesa just before the harbour closed, reports American Journal of Transportation.

At least five merchant ships have been blown up in the region since the attack started, highlighting the risk that the crews are facing.

Vessels can't leave Ukrainian waters because there are no harbour pilots to guide them out, according to owners and ship managers. More importantly, navigation in parts of the northwest Black Sea is restricted due to the threat posed by underwater mines, according to an alert posted on the Spanish Navy's website.

At least some of the stranded vessels have cargo on board, according to people with knowledge of the vessels in the area.

Panama-flagged cargo ship Helt sank after being hit below the waterline, prompting rescue operations to bring ashore six crew, said Ukraine's Administration of Sea Ports. Meanwhile, an engineer on Bangladesh Shipping Corp's vessel Banglar Samriddhi died when a missile hit the ship.

"All ports are blocked," said Henrik Jensen, managing director of Danica Crewing Specialists, which provides services to two ships stuck in Ukraine with 40 crew on board, all of whom are uninjured. "This is a terrible situation."