The main militant group responsible for a string of recent attacks in Nigeria's southern oil-producing Niger Delta region says it has sabotaged another pipeline belonging to the British-Dutch Shell oil company.

In an e-mailed statement, the Movement for the Emancipation of the Niger Delta says its fighters attacked the pipeline late Thursday.

It would be the fourth Shell pipeline the group has attacked this month. Shell officials have not confirmed the incident.

Militants and gangs began attacking oil facilities in the Delta in late 2005 to demand that more oil revenue be directed to impoverished local residents.

The attacks have reduced Nigeria's daily oil output by an estimated 20 percent. The loss of production has contributed to the spike in world oil prices.

Some information for this report was provided by AP and Bloomberg.