One of the offshore oil facilities of Exxon Mobil off Nigeria's coast was attacked by gunmen over the weekend.

The attack came seven day after London-based oil exploration firm Afren said gunmen attacked its offshore oil rig and abducted seven crew members.

In a statement sent to Xinhua on Monday, Exxon Mobil said one of its offshore facilities was boarded by unknown armed persons in the evening of Sunday.

"Relevant Government and security agencies have been informed and appropriate response measures are underway at this time," the company said.

"We restate our commitment to ensuring the safety of people and property," it added.

No militant group has claimed responsibility for the attack.

Last Monday, Nigeria's main militant group, the Movement for the Emancipation of the Niger Delta ( MEND), warned that its fighters will launch a series of attacks on oil installations across the oil-rich Niger Delta region in the coming days.

The group has been known for carrying out attacks on international oil companies in the Niger Delta, engaging in actions including sabotage, theft, property destruction, guerilla warfare and kidnapping.