At least twelve people have drowned when their boat sank off an island in western Greece, marking the deadliest toll in months in the country's migrant crisis.

Twenty one people were rescued on Saturday, the Greek coastguard said.

Helicopters and ships were searching the area southwest of the island of Paxos for more survivors.

Medical staff transfer a survivor from an ambulance to hospital. Credit:

Authorities said they had accounts of up to 50 people being on the vessel.