"There was an attack on a Chevron facility near Escravos on Wednesday night. The incident happened about four nautical miles from Escravos, near Warri, in Delta state," spokesman Chris Ezekobe told AFP.
Ezekobe said "militants using explosives blew up the Okan platform, a collection facility for offshore oil and gas that feeds the Escravos terminal".
He said it was not known how many people were on the platform at the time, but that there were no known casualties.
"A previously unknown group called the Niger Delta Avengers has claimed responsibility for the incident," the spokesman said, confirming a statement on the group's website.
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"But we are not ruling out the involvement of former Niger delta militant leaders, particularly Tompolo, who is wanted on fraud charges."
Chevron Nigeria Limited (CNL), which operates the joint venture with Nigeria's state-run oil firm, confirmed in a statement that the facility was attacked at 11:15 PM (local time) on Wednesday.
The company blamed "unknown persons" for the breach, adding: "The facility is currently shut-in and we are assessing the situation, and have deployed resources to respond to a resulting spill."
"CNL continues to monitor the situation and remains committed to meeting its business and corporate obligations, including protecting people and the environment and conducting its operations reliably and safely."
There was no immediate indication of the volume of crude affected but a Chevron official, who asked not to be identified, said the attack would hit gas supply to power plants already affected by almost daily outages.
Attacks on oil and gas facilities have increased since January when Tompolo -- whose real name is Government Ekpemupolo -- was declared wanted on multi-million-dollar corruption charges.