Militants attacked a crude oil pipeline operated by Italy's ENI on Saturday, a Nigerian state government said, hours after the Niger Delta Avengers militants claimed another strike in the region.

Nigeria's oil output has fallen to a 20-year low due to attacks on pipelines in the southern swamps, home to much of its hydrocarbon resources, which have compounded the impact of low oil prices on Africa's largest economy.

"The Bayelsa State Government has condemned in its entirety the attack on a trunk line belonging to Agip (ENI) by (a) new militant group, the Niger Delta Avengers," it said in a statement. Bayelsa lies in the Delta region.