Twin car bombs exploded outside a government building where amnesty talks were underway Monday in Nigeria's restive and oil-rich region, wounding two people and causing panic, a government spokesman said.

Monday's bombing is the most daring attack claimed by the Movement for the Emancipation of the Niger Delta since the group abandoned an unconditional cease-fire agreement with the government. It also may signal the end of amnesty negotiations that have fallen apart during the long illness of Nigerian president Umaru Yar'Adua, who brokered the deals before his health worsened.

On Monday, MEND, which is the most prominent militant group in the Niger Delta, promised more attacks.

In a statement e-mailed to reporters minutes before the bombing, MEND said the bombs were part of a new wave of attacks that would sweep across the Niger Delta.

"The deceit of endless dialogue and conferences will no longer be tolerated," the group's statement read. "The lands of the people of the Niger Delta was stolen by the oil companies and northern Nigeria with the stroke of a pen."

Delta state spokesman Linus Chima told The Associated Press just before the bombing that "there is nothing to worry about at all." A live broadcast of the event carried by African Independent Television, a Nigerian satellite channel, showed officials did not evacuate the government building after receiving the warning.

On the live broadcast, an explosion could be heard in the background, halting a speaker in mid-sentence. A man's voice then urged those inside to remain calm.

Later television footage showed flames and smoke rising from a nearby roadway. Witnesses said the blasts blew out windows in the meeting room.

Chima said it appeared that the two bombs were placed inside cars near where a Nigerian newspaper, Vanguard, was helping hold a discussion with government officials about an amnesty deal offered to militants in the region. The spokesman said two people were wounded and that he had no other information. Yelling could be heard in the background during the telephone call.

"I think it was a deliberate attempt to sabotage the peace talks," Chima said.

MEND has used car bombs before. In April 2006, MEND claimed responsibility for two car bombs at an army barracks and an oil refinery in which two people were killed. It also detonated a car bomb outside a state governor's office in December 2006.

Analysts have questioned MEND's capabilities in the weeks after the group announced it had called off its cease-fire with the government. State governments and oil companies later denied the group carried out attacks it had claimed responsibility for in statements to reporters.

MEND seemed to address those questions in its statement to reporters.

"In the coming days, we will carry out a number of attacks against installations and oil companies across the Niger Delta and will spread out to companies such as (French oil company) Total which have been spared in the past," the group said in an e-mailed statement. "We hope the actions which will follow will persuade ... (officials) that we exist outside of cyberspace."

Militant groups in the Niger Delta have attacked pipelines, kidnapped petroleum company employees and fought government troops since January 2006. They demand that the federal government send more oil-industry funds to Nigeria's southern region, which remains poor despite five decades of oil production. They also criticize the oil giants for polluting their rivers with spilled oil and flared excess gas produced when drilling.

The region became peaceful after negotiations began for the government-sponsored amnesty program, which planned to offer cash payoffs for militants to abandon the fighting. Some militants also heralded Goodluck Jonathan becoming acting president as a positive sign, as he is the first Niger Delta politician to take over the country's highest office. However, many militants have grown restless in recent weeks as they say the government has stalled the peace process.