The main militant group in Nigeria's oil-producing Niger Delta says it attacked a military helicopter near a major rebel camp on Thursday. From the Nigerian capital, Abuja, Gilbert da Costa reports the group is warning that it will resume hostilities if it is provoked by the military.

The Movement for the Emancipation of the Niger Delta says a military helicopter gunship, which flew close to a major rebel camp in Bayelsa state, came under fire from what it called "heavy anti-aircraft guns." The rebels claim the aircraft was severely damaged and may not have made it back to base.

A military spokesman in the region, Lieutenant Colonel Rabe Abubakar, told VOA a military helicopter gunship was in the area on reconnaissance. Colonel Abubakar said the military acted on intelligence that some criminal gangs were stealing crude oil, and some militants were planning to attack facilities owned by Royal Dutch Shell.

"Actually there was a recce [reconnaissance] by our helicopter," he said. "The recce was based on the information that we received in respect of illegal international oil bunkering [theft].  Another reason was the threat by some militants to bomb Shell facilities. Based on these tip-offs, we had to go on a recce."

The U.S. oil company Chevron says it will not be able to meet its delivery obligations in exports from its Escravos oil terminal in the Niger Delta until the end of the year, after a militant attack on a key pipeline.

The commander of a special military unit said government troops in the Niger Delta repelled an attack Thursday by gunmen close to the Escravos terminal.

Attacks by armed groups in the Niger Delta, Nigeria's main oil-producing region, have cut more than 20 percent of the country's crude exports since 2006.

MEND declared war on the oil industry in September in response to what it said was an unprovoked attack by the army on one of its positions. The group announced a ceasefire last month.