ABUJA, Nigeria — Nigeria's Senate has ordered a subsidiary of petroleum giant Royal/Dutch Shell to pay a Nigerian ethnic group US$1.5 billion (euro1.2 billion) for oil spills in their homelands, but the legislative body can't enforce the resolution, an official said Wednesday.

Nigeria's Senate ruled Tuesday that the unit, Shell Petroleum Development Company of Nigeria Ltd., must disburse the payment over five years to the Ijaw people of Nigeria's oil-flush south as compensation for pollution in their area since 1956, Senate spokesman Henry Ugbolue said.

He acknowledged the senate had no power to enforce such a resolution, Ugbolue said. However, he suggested that President Olusegun Obasanjo might be able to enforce the order.

"The leadership of the Senate is committed to ensuring that the order is obeyed, and I am sure they will do everything to prevail on the executive to enforce the order," Ugbolue said.

Shell said in a statement it hadn't received the resolution and couldn't comment on it.

The Anglo-Dutch firm is the biggest oil company in Nigeria, accounting for half of the 2.5 million barrels pumped daily here. Nigeria is Africa's largest oil exporter, the world's seventh-largest oil exporter and the fifth-biggest source of U.S. oil imports.

The Ijaw people and others in Nigeria's oil-rich Niger Delta have long complained that oil companies' operations pollute their region's creeks and rivers. They remain among the poorest people in Nigeria despite the area's vast petroleum stores. Thiefs frequently tap into region's pipelines and steal crude to sell, sometimes igniting deadly explosions and fouling lands.