"The military has received information of an attack and have deployed its men to Abonema to verify the truth of the claim and we can not sustain it at the moment," Timothy Aneigha, the spokesman for the military joint task force that operates in the Niger delta, said.
Mend said that the attack was in response to the government using the ill-health of Umaru Yar'Adua, the president, to stall talks aimed at ending the long-running unrest in the Niger delta region.
Yar'Adua, who is said to be suffering from acute pericarditis, an inflammation of the membrane covering the heart, has been in hospital in Saudi Arabia since November 23.
"While the Nigerian government has conveniently tied the advancement of talks on the demands of this group to a sick president, it has not tied the repair of pipelines, exploitation of oil and gas as well as the deployment and retooling of troops in the region to the president's ill health," it said.
"While wishing the president a speedy recovery, a situation where the future of the Niger Delta is tied to the health and well being of one man is unacceptable," it said.
Charles Dokubo, an associate professor at the Nigerian Institute of International Affairs, said that he did not believe that Mend would abandon the peace process with the government.
"They realise that the solution to the Niger delta problem can only be through dialogue," he told Al Jazeera from Lagos.
"If they say they are going to tear the amnesty agreement into shreds, that is just a bargaining position."
Mend, the main umbrella group in the region, says it is fighting for a greater share of the region's oil wealth for the local communities in the Niger delta.
But following the amnesty it named a team to hold negotiations with the government, while Yar'Adua's administration pledged to spend billions of dollars developing the region after thousands of armed men accepted the presidential amnesty.
Earlier this week, the government announced the creation of five committees that will address oil, environmental and disarmament issues in the delta.
At the peak of the unrest Nigeria, the world's eighth largest exporter of crude, saw its output slashed by a third.
But since the amnesty deal, Nigeria's oil output has risen to around 1.98 million barrels per day, according to latest report from the International Energy Agency.