The overnight attack in southern Rivers State was against two pipelines believed to be owned by a unit of Royal Dutch Shell PLC, The Movement for the Emancipation of the Niger Delta leader said on condition of anonymity to avoid capture by authorities.
Shell said in a statement to The AP that its local joint venture had been informed of an "incident" on a pipeline. It said it had no more details pending an investigation.
The militants' campaign against oil infrastructure and staff in Africa's biggest oil industry have cut production by about one quarter, helping send crude prices to all-time highs in international markets.
The militants say they're acting to force the Nigerian federal government to send more oil-industry funds to the southern region, which produces all of Nigeria's crude oil but remains impoverished after decades of corrupt and wasteful governance.
The militants ended a unilateral cease-fire in recent weeks after what they branded interference by foreign governments offering to help the Nigerian government quell unrest in the southern Niger Delta. The group also seeks the release of one of its leaders who is on trial for terrorism and treason.
The government acknowledges a need for development in the Niger Delta, but considers the militants little more than criminals who profit from the highly lucrative theft of crude oil, which is siphoned from pipelines and shipped overseas for resale.