Earlier in the week, Shell confirmed its Alakiri flow station had been the subject of one attack and a second had targeted the Greater Port Harcourt Swamp Line.

Shell later neither confirmed or denied claims of attacks on its Orubiri flow station, Rumuekpe pipeline and another pipeline at the Elem-Kalabari
Cawthorne Channel axis in Rivers state.

Chevron has confirmed two "shooting incidents" near its facilities and it had no reason to believe it was specifically targeted in either attack.

'Oil war'

Jomo Gbomo, a Mend spokesman, on Saturday claimed to have grassroots support: "The impoverished and neglected inhabitants of oil-producing communities consider our actions to these structures as good riddance to bad rubbish.

"Oil exploration has brought only pain to them by way of environmental damage, harassment from the military and rape of under-aged girls by soldiers, extra-judicial killings of young men and development and wealth to other parts of the country at their detriment," he said.

Mend has also warned it will attack the country's two big deep offshore fields, Shell's Bonga and Chevron's Agbami, as well as oil and gas tankers in Nigerian
waters.

The latest attack claimed by Mend was cited as a factor in Friday's rise in world oil prices to more than $100 a barrel.

But analysts said the predominant reason was an improvement in market confidence after efforts to resolve the US-centred world financial crisis which brought predictions of further falls in oil demand.

Insecurity in the region has cut the West African country's output by around a fifth since early 2006, when Mend began blowing up oil pipelines and kidnapping foreign workers, helping push up world oil prices.

The Niger Delta accounts for most of Nigeria's oil output of two million barrels per day, making it the world's eighth-biggest oil exporter.

Royal Dutch Shell, ExxonMobil, Total, Eni, and Chevron, are among the numerous oil companies operating in the Niger Delta.