Four Turkish nationals have been abducted in western Nigeria, local police have told the BBC.

The four, who are construction workers, were kidnapped by gunmen at a bar in Kwara State on Saturday night.

An operation to try to rescue them is underway. No group has said it carried out the abductions.

Last week pirates attacked a cargo ship off the coast of Nigeria and kidnapped 10 Turkish sailors. Their fate remains unknown.

Kidnapping for ransom is common in Nigeria, with foreigners and high-profile Nigerians frequently targeted.

In April, a prominent politician and his daughter were abducted on a highway in Kaduna State. They were released after ransom was paid.

In the same month, two kidnappings targeted foreigners. In the Niger Delta region, gunmen kidnapped two senior Shell workers and killed their police guards. A British woman was shot dead in Kaduna when armed men stormed a holiday resort. They killed one other person and kidnapped three during the attack.

In January last year, two Americans and two Canadian citizens were abducted while travelling from the town of Kafanchan in Kaduna state to the capital Abuja. Two of their police escorts were killed.

The four kidnap victims were later freed unharmed in a joint military and police operation.