"Seven expatriates were kidnapped," said a security source in Nigeria on Friday. Other hostages were Colombian and Russian, the source added.

A British embassy spokesman confirmed that a Briton had been involved in "an incident" in the southern delta region where most of Nigeria's crude oil is produced.

Nigeria is Africa's largest producer of crude oil, with a daily export quota from the OPEC oil cartel of more than two million barrels per day.  

The hostages work for a pipeline coating company called Brodero Shaw, a security source said. "At the moment (the company) is in discussions with the governor to have them released," the source added.

Nigerian and expatriate oil workers are often kidnapped by pirates and local tribes but - although the oil firms deny paying ransoms - they are usually released unharmed.