Nigeria's main rebel group, the Movement for the Emancipation of the Niger Delta (Mend), is threatening to call off its ceasefire with the government if foreign oil companies do not leave their land.

Henry Okah, the group's leader, told Al Jazeera's Yvonne Ndege that the government has not stuck to its part of the deal and that "there will be a resumption of violence very soon".

Many of the armed groups argue that they are fighting for a greater share of oil revenue to remain in the Niger delta and complain of the pollution caused by the industry.

Attacks on pipelines and industry facilities - along with the kidnapping of oil workers - since early 2006 have cost the world's eighth-biggest oil exporter billions of dollars a year in lost revenues and added to volatility in global energy prices.

Dora Akunyili, the Nigerian minister of information, told Al Jazeera: "We need to establish peace in that region. It is only when peace is established that meaningful dialogue can follow and sustainable development would naturally be in place".

Click here to watch Henry Okah's exclusive interview with Al Jazeera: