Hampshire Police said on Thursday night the men, who smuggled themselves onto the Nave Andromeda in Lagos, were released from custody pending further investigations.

But they "remain detained under Border Force powers", police said in a statement.

The men were arrested on suspicion of "seizing or exercising control of a ship by use of threats or force" after a mayday call forced a special forces raid on the 43,000-tonne tanker.

Detectives have said they threatened the 22-member crew, forcing them to seek sanctuary in the ship's citadel, from where they raised the alarm.

The Liberian-flagged, Greek-owned vessel, which was six miles (10 kilometres) off the Isle of Wight on England's south coast at the time, was taken to the port of Southampton.