Four people, believed to be British, have been kidnapped in Nigeria's southern Delta state, police in the country have said.

The four were reportedly taken at about 02:00 local time on Friday when suspected militants stormed a rural community they were living in.

The Foreign Office has not commented.

Andrew Aniamaka, a police spokesman in Nigeria, said officers had identified a militant group, calling themselves the Karowei, as the main suspects.

No ransom demand had yet been made, he added.

BBC reporter Stephanie Hegarty, based in the Nigerian commercial capital Lagos, said police believe the reported kidnapping could be a response to a recent surge in efforts to tackle militancy in the region.

She said kidnapping for ransom is common in the oil-rich Niger Delta area.

The UK Foreign Office currently advises against all but essential travel to parts of southern Nigeria, saying there is "a high threat of kidnap throughout Nigeria".