An executive of the US oil service company Baker Hughes was killed in an apparently targeted attack in Nigeria's south-eastern oil city of Port Harcourt on Wednesday, authorities said.
It was not immediately clear if the attack was related to a five-month campaign by Niger Delta militants to cripple the oil industry in the world's eighth largest exporter, but a diplomat and an oil company source said they thought not.
"The American was shot by a man on a motorcycle. The motorcycle pulled up beside him and shot him," Rivers State Police Commissioner Samuel Agbetuyi told Reuters.
The Houston-based company, which drills oil wells and performs other services for big oil companies, was not immediately available for comment.
An oil company source said the gunman on the motorcycle appeared to be working in co-ordination with a car, and it looked like a targeted assassination of the American, who held a managerial role in the company.
Militants from the Movement for the Emancipation of the Niger Delta (MEND), whose attacks have cut Nigerian oil exports by a quarter, threatened this week to carry out attacks on oil industry targets and individuals. However, they have treated American oil workers well during kidnappings, and the Port Harcourt killing did not bear any similarity to previous MEND attacks.
The oil industry source said Baker Hughes had decided to pull its staff out of Port Harcourt to Lagos as a security precaution.
Port Harcourt is the largest city in the delta, and several oil multinationals have major offices there, including Royal Dutch Shell and Agip.