A rebel deadline has passed for the release of the leader of a militant group in Nigeria's troubled Niger Delta. The group's members are threatening to destroy government property and oil facilities unless he is released by authorities.

Members of the banned militant group known as the Niger Delta People's Volunteer Force, or NDPVF, have warned foreign oil workers to leave the area, as they prepare to retaliate for the arrest of their leader.

Group members say Moujahid Dokubo-Asari was arrested Tuesday by soldiers and police in his office in the Niger Delta's major city, Port Harcourt. Police say Mr. Dokubo-Asari is being questioned for comments allegedly calling for Nigeria's disintegration.

Gunfire was heard throughout the night as his supporters began to mobilize. And early Wednesday, NDPVF commander Dakuro Princewill set a deadline of two oclock in the afternoon local time for Mr. Dokubo-Asari's release. Mr. Pricewell said thousands of militants were ready to arm themselves and retaliate against the government and foreign interests.

The leader of another militant group known as the Ijaw Youth Council, Miadiye Kuromiema, says he expects a swift response from federal security forces.

"The direct response [of] the federal government is a crackdown," said Miadiye Kuromiema. "The federal government has always used every opportunity to terrorize the people to quietness."

The Niger Delta has long been the scene of violent confrontations between federal security forces and armed groups, who are demanding a greater share of petroleum wealth and blame foreign oil companies for destroying the local environment.

Tensions have been running high following the detention last week in London of Bayelsa state Governor Diepreye Alamieyeseigha over corruption allegations. His passport is being held by British police pending developments in the case.

The governor's supporters in the Niger Delta accuse President Olusegun Obasanjo of using an anti-corruption campaign to get rid of political enemies.

West Africa political analyst Olly Owen is currently in Port Harcourt on a research trip. He says the arrest of the militia leader Tuesday may have been taken as a preventative measure.

"The government in Nigeria might be taking preemptive action in detaining Mr. Dokubo-Asari," said Olly Owen. "That might be a preemptive action. At the moment, I don't think that anything direct is likely to happen on the ground in terms of major developments."

Mr. Owen says real acts of violence and sabotage have, in the past, rarely been signaled beforehand. And he says, there is reason to believe that will be the case again.

"When you look at the incidents where workers of foreign oil companies have been kidnapped in the past, it's generally by the local communities or local militia groups," he said. "Actually, when things are said at a higher political level, they tend to be more in the field of rhetoric and are more symbolic statements."

Last year, Mr. Dokubo-Asari helped send world oil prices to record levels with threats to unleash a full-scale war on international oil firms. He scaled back those threats after holding direct meetings with President Obasanjo.