Five Polish sailors, including the ship’s captain, have been kidnapped from a vessel off the Nigerian coast in a suspected act of piracy.

Witold Waszczykowski, Poland's foreign minister, said the cargo ship Szafir, on route from Antwerp to the Nigerian port of Onee, was attacked on Thursday night by a group of “unknown” assailants 30 nautical miles from land.

"During the night there was an attack on a Polish ship when a group unknown to us boarded the vessel,” said the minister at a press conference.