Two car bombs shook a government building hosting amnesty talks in the southern Nigeria oil town Warri Monday, minutes after militants issued a bomb threat.

The Movement for the Emancipation of the Niger Delta (MEND) said in an emailed statement prior to the detonations that its operatives had planted three bombs in the compound of the building.

MEND has rejected a government amnesty aimed at ending years of unrest and sabotage in the oil-producing Niger Delta.

Local government officials said that two cars exploded outside the compound, shattering the windows of the building. No injuries were reported.

The group gave only 30 minutes notice of their intention to detonate the bomb and allow evacuation.

Several state governors were attending the conference, which was organized by the Vanguard newspaper group and aimed at discussing the post-amnesty environment.

MEND spokesman Jomo Gbomo warned this was the beginning of a new onslaught.

'In the coming days, we will carry out a number of attacks against installations and oil companies across the Niger Delta,' he said in a statement.

MEND says it is fighting for a share of oil revenue for Niger Delta residents, who complain that multinational oil companies have ruined their agriculture and fishing livelihoods and caused environmental damage in the deltas creeks.

Attacks by militant groups had slashed Nigeria's oil production by around a quarter from 2006 levels, allowing Angola to overtake it as Africa's biggest oil producer.