Most groups have adhered to a ceasefire in the last few weeks while the government held talks with community leaders who, like the militants, want a greater share of Nigeria's energy wealth to go to the region that produces most of its oil.
"The Niger Delta Avengers cannot be blamed for the continuous bombing of crude oil export pipelines and other oil installations, since the government has been relentlessly carrying out military build ups to continuously harass communities," the NDA said on its website.
President Muhammadu Buhari sent army reinforcements in May to hunt down militants, a move that stoked anger as residents complained of rape, looting and arrests of youths unrelated to the militants, charges denied by the military.
On Nov. 1, Buhari met leaders from the region for the first time since the attacks began. They urged him to withdraw the army, order oil firms to move their headquarters there and spend more on development to end the militancy.
Buhari, a former military ruler, responded by saying he would "revisit the situation" in the Niger Delta once he had considered reports from armed forces chiefs. But militants, including NDA, have attacked oil facilities since the talks.
"The High Command of the NDA is only reacting to government's deliberate attempts to undermine the process to dialogue and negotiations," the NDA said in its statement.
It said "the path to sustain the cessation of hostilities in the region" could not be achieved "when there are clear cases of deliberate security surge by the Nigerian government".
Attacks since the start of the year cut the OPEC member's oil production by more than a third in the summer.
But, with attacks becoming less frequent in the last few months, the oil minister said output had recovered to 2.1 million barrels a day. That brought it roughly back to levels before the attacks began.