Security forces in Nigeria say they have killed or arrested several criminals in a pre-dawn attack on a gang operating in the southern oil city of Port Harcourt.   Sarah Simpson reports for VOA from Lagos the raid follows last week's fighting between armed gangs.

Gunfire continued through the morning on the streets of Port Harcourt, after security forces launched a surprise assault on one of the criminal gangs they say is behind a six-day turf war.

A military spokesman said a special Joint Task Force of military and police attacked the camp of gangland leader Soboma George.  George is linked to the militant group the Movement for the Emancipation of the Niger Delta.

The group is responsible for the majority of attacks on oil installations that have forced Nigerian oil production down by 25 percent since early 2006, helping force up oil prices worldwide.

The military confirmed they arrested and killed some of their targets, declining to give numbers or details.

Armed gangs locked into battle last week, forcing much commercial activity in Port Harcourt to a halt.  Police have confirmed 12 deaths in the gang fighting, but local newspapers put the death toll many times higher.

The international charity Doctors Without Borders says that their clinic in Port Harcourt has treated 71 people for gunshot wounds during the past two weeks, seven of whom died of their injuries.

Militant groups say that they are fighting for a greater share of Nigeria's multi-billion dollar oil wealth to go to the impoverished states where it is produced.

But the Niger Delta violence is increasingly linked to criminal gangs fighting for a share of ill-gotten gains.  Tapping of oil pipelines that criss-cross the region to siphon off crude, a practice known as bunkering, is common, as is hostage-taking of foreigners or relatively wealthy Nigerians, for ransom demands.