Gunmen shot dead an 11-year-old Nigerian girl and abducted her nine-year-old brother as they walked to school in the southern oil city of Port Harcourt yesterday, police said.

Their father works for Anglo-Dutch energy giant Royal Dutch Shell in Port Harcourt, the hub of Africa's top oil and gas industry, a company spokesman said.

The attackers shot the girl as she tried to prevent them from dragging her brother into a car in the Rumuokwuta area of central Port Harcourt, the capital of Rivers state.

"A red Honda car intercepted them on the way (to school). The gunmen came out of the vehicle and grabbed the boy," said a police spokesman for Rivers.

"While the sister was struggling with them, she was shot. The gunmen went away with the boy. Passers-by rushed the girl to hospital but she died on the way."

Foreign companies in sectors ranging from telecoms to construction, as well as the oil industry, have pulled out expatriate workers, hindering the completion of badly needed infrastructure projects such as new roads and electricity.

The militants' tactics, which include kidnapping foreign oil workers and blowing up pipelines, have turned parts of the delta into a military zone as the security forces set up checkpoints and mount air and sea patrols to fight them.

Criminal gangs have taken advantage of the breakdown in law and order, carrying out kidnappings for ransom, armed robberies and vehicle hijackings which have left the region's residents living in a state of permanent insecurity.

Hundreds of foreign oil workers have been kidnapped in the Niger Delta over the past three years, most of them released unharmed after the payment of a ransom.

But abductions have increasingly targeted Nigerians, making a mockery of the militants' claims to be fighting for the development of the region.

Police said yesterday that a Catholic priest, kidnapped by gunmen at the weekend, had been released.

But fighters have regularly abducted oil workers themselves and the security forces say its camps in the delta's creeks harbour the gunmen responsible for rising crime. Two Britons, seized more than four months ago, are still being held by their captors.