The Niger Delta Avengers have pledged to lay down their weapons and resume talks with the Nigerian government after months of attacks on the country's oil and gas infrastructure that have crippled the economy.
In a message posted on the group's website late on Saturday, the NDA said it would "observe a cessation of hostilities" in the Niger delta.
It also said it would support any effort to negotiate with "the federal government of Nigeria, representatives from the home countries of all multinational oil corporations and neutral international mediators."
There have been unconfirmed reports for several weeks of talks under way between Abuja and the NDA, but the rebel group never publicly acknowledged that it was engaged in negotiations.
The NDA pledged to observe "our cessation of hostilities ... unless the ruling political APC (All Progressives Congress party) continues ... to arrest, intimidate, invade and harass innocent citizens and invade especially Ijaw communities."
The Ijaw ethnic people have long dominated oil rebel groups operating in the area, though experts say militants from other communities have also set up new branches.
Since the start of the year, the NDA has carried out a string of devastating attacks on Nigeria's oil pipelines and facilities.
Oil majors including Shell, Exxon, Chevron, Eni and the state-run oil group NNPC have all been targeted this year.
The attacks have reduced Nigeria's output by a third, hammering government revenue at a time of low global oil prices.
The oil sector accounts for 90 percent of the nation's foreign exchange earnings and 70 percent of government revenue.
The NDA has claimed to seek a fairer share of Nigeria's oil wealth for residents of the region as well as self-determination and political autonomy.