Police in Nigeria say gunmen have attacked a US convoy, killing four people, including two personnel from the US consulate and two police officers.

Three others were kidnapped before their vehicle was set on fire.

The attack took place in south-eastern Anambra state. A rescue and recovery operation is under way.

No US citizens were in the convoy and there were no details regarding the convoy’s presence in the state.

A Nigerian state police spokesperson expressed regret that the convoy entered the state “without recourse to the police in the area or any security agency”.

The US said its mission in Nigeria was working with Nigerian security services to investigate the incident.

“The security of our personnel is always paramount, and we take extensive precautions when organising trips to the field,” the US State Department said.

Violence in the south-east of the country is just one of the many issues facing president-elect Bola Tinubu, who takes the helm of Africa's most populous nation later this month..