The Movement for the Emancipation of the Niger Delta (Mend) said on Thursday it had killed 17 soldiers in separate firefights in the Niger Delta on Wednesday but said it would scale back its operations.
A Mend spokesman said: "This whole thing wasn't supposed to happen this way. We were still in the concluding stages of our plans to completely halt Nigerian exports in one swipe.
"We are watching the Nigerian military and our actions will be governed by measures they choose to take.
"We have been forced now to act ahead of schedule," he added, referring to a flare-up of violence on Monday which began when about 70 gunmen from a separate group attacked a convoy of boats supplying Royal Dutch Shell oilfields.
The men killed at least three soldiers and abducted 25 Shell contractors who have now all been freed.
Mend has been threatening all year to halt Nigerian exports completely but has yet to show it can carry out the threat.
Oil worker killed
A Nigerian oil worker was killed during an attack by gunmen on ships belonging to the Italian oil company Agip in the Niger Delta, the company said on Thursday.
Agip, a subsidiary of the Italian oil giant Eni, said in a statement that "armed men in five boats" attacked a convoy of seven boats ferrying supplies and food from Nigeria's oil capital Port Harcourt to the southern city of Brass on Wednesday.
A company statement said a Nigerian employee of Agip was "accidentally hit by the assailants, who were targeting the engines, and was killed during the attack."
In a separate incident, gunmen invaded a residential compound for contractors to ExxonMobil on Tuesday night, killing two Nigerian security guards and kidnapping four Britons, a Romanian, a Malaysian and an Indonesian.
A diplomat said on Thursday they were in good health and their kidnappers had demanded a ransom for their release.
Olusegun Obasanjo, Nigeria's president, has met senior army chiefs and the governors of two Niger Delta states, Rivers and Akwa Ibom, to discuss the situation at the presidential villa in Abuja.
The army chiefs declined to comment on the outcome of the talks but Akwa Ibom Governor Victor Attah said he had argued against a military crackdown.
Attah said: "We have to dialogue with the people to know what they want and in this case they just want development, empowerment and opportunities for employment."
Lumumba Okugbawa, acting secretary general of the Petroleum and Natural Gas Senior Staff Association of Nigeria, a Nigerian trade union, said: "These kidnappers can't be doing it on their own, without support from a powerful cabal that cuts across state and local governments and even the armed forces."