The Niger Delta Avengers militant group on Thursday said it attacked more oil infrastructure in southern Nigeria, ignoring a call for unity from President Muhammadu Buhari.

The group said in an email that it hit manifolds RMP 22, 23 and 24 operated by Chevron Nigeria Limited in Delta state at about 1:20 am (0020 GMT). RMP 23 and 24 had previously been attacked on June 1. 

RMPs or remote manifold platforms are where smaller oil and gas pipelines converge before being sent to larger lines.

It is understood the facilities had been repaired since the last strike.

A military officer said the attack happened in the Warri North area of Delta state, adding: "A controlled explosive device was used to carry the attack.

"These gives them (the militants) ample time to detonate the device even while they have long left the scene of the incident."

The spate of attacks claimed by the Niger Delta Avengers since February has hit oil production in Nigeria, exacerbating a financial crisis caused by low global crude prices since mid-2014.

The group wants international oil companies out of the region, whose people largely live in poverty despite the billions of dollars generated by oil extraction over decades.

It has also called for self-determination for the delta region.

Buhari on Wednesday appealed to militants to "give Nigeria a chance" at a time of economic hardship -- and that he would not stand for a break-up of the federation.