(CNN) -- Nigeria's main militant group issued a veiled threat Monday against an upcoming world football tournament that is tentatively scheduled to take place in the west African nation later this year.
Militants from the Movement for the Emancipation of the Niger Delta, pictured September 2008 in the Niger Delta.
The Movement for the Emancipation of the Niger Delta warned the international football association FIFA that it should "rethink" allowing Nigeria to host the upcoming under-17 World Cup series later this year.
"The safety of international players and visitors can not be guaranteed due to the current unrest," MEND said in an e-mail.
Only two out of the nine stadiums in Nigeria are close to being ready for the tournament which is scheduled to take place between October 24 and November 15, according to FIFA. The association has given the country a grace period to start constructing the remaining venues, FIFA Vice President Jack Warner said.
In its e-mail, MEND claimed to have attacked a Chevron oil station in the Niger Delta region Monday as part of its latest offensive against the Nigerian government, dubbed "Hurricane Piper Alpha."
"Hurricane Piper Alpha hit the Abiteye flow station operated by Chevron today, Monday, June 15, 2009 at about 0200 Hrs triggering another 'systems failure' which resulted in a massive fire outbreak that is consuming the entire facility," MEND said.
It threatened further attacks in other states in the Niger Delta region, as well as offshore oil facilities.
Chevron, which halted its onshore operations in the region last month, said it is investigating the reported attack on its Abiteye flow station.
"We are working to ensure the safety of our people, restore the integrity of our operations as soon as possible and are not speculating on any comment while investigations are being undertaken," according to an e-mailed statement from Chevron spokesman Scott Walker.
Last month, the militant group declared an "all-out war" on the government after what it said was a deadly bombing raid on civilians.
It is not the first declaration of war by MEND, which demands that more of Nigeria's oil wealth be reinvested in the region instead of enriching those whom the militants consider corrupt politicians.
The militant group declared war against the government in September for what it said were unprovoked attacks. At that time, MEND destroyed several oil facilities, forcing Nigeria to cut its oil exports by as many as 1 million barrels of oil per day, or 40 percent.
The recent violence -- which has included attacks on pipelines and hostage-taking -- has limited shipment of crude oil supplies out of Nigeria, Africa's largest producer.