A Nigerian militant group threatened on Monday to step up attacks on oil facilities in the Niger Delta if the president pursues a military campaign, casting a shadow over peace talks between the government and groups due to start on Tuesday.

In written responses to Reuters questions, Mudoch Agbinibo, spokesman for the Niger Delta Avengers (NDA), said President Muhammadu Buhari must “come down from…his iron-horse of ethnic and religious bigotry”.

On Tuesday, Buhari is due to meet Niger Delta leaders and representatives of various militant groups in Abuja, the first time since the government began a dialogue in June to end a wave of attacks on oil facilities that has crippled output.

The stakes are high as the OPEC member badly needs peace in the impoverished swamp land to bring back oil output, which at its lowest point halved from 2.2 million barrels per day in January, to drag Africa’s biggest economy out of recession.

Analysts say the NDA are the region’s most sophisticated militants and receive help from inside oil firms advising which facility to attack. Their divers blew up a Shell undersea pipeline, which stopped up to 300,000 bpd overnight.

Agbinibo said the group was “determined to gradually grind the flow of our oil” if Buhari’s administration opted to continue its military campaign in the southern region.

Buhari ordered a heightened military presence in the restive region in May which saw the introduction of patrols in remote communities which has stoked anger in the last few months.

An offensive targeting militant camps launched in August led to the deaths of five people and the arrests of 23 others. The death of an ex-militant leader’s 84-year-old father due to injuries allegedly sustained in an army raid marked a flashpoint.

“Any plan of the Nigerian government thinking of exploiting the resources of the Niger Delta to fund…government without our genuine involvement will be a very tall dream,” said the spokesman who carries the title of “Brigadier General”.

There was no immediate comment from the Nigerian government.

The comments come comes days after the Avengers claimed a strike on a Chevron pipeline last week – only the second since saying in August they would cease hostilities to pursue talks. They said it was carried out as a warning to oil companies.

The Avengers want a greater share of Nigeria’s oil wealth to be directed to the impoverished southern swampland Delta region, which produces most of the crude oil whose sales account for around two-thirds of government revenue.

The NDA spokesman said the group was a “liberation movement, poised towards the control of our resources” that would “pay appropriate tax to the central government”.

The secretive group had so far avoided talking to foreign media, announcing only attacks and often lengthy and rambling statements resembling lectures on Nigerian history on social media and its website.

There is no phone number to call them, only an anonymous email account. Agbinibo has previously sent details of attacks directly to Reuters which have later appeared on the group’s website – its primary means of communication.

The last administration in 2009 ended a previous Niger Delta insurgency by offering cash, contracts and job training for those fighters who stopped blowing up pipelines.

The militants resumed their fight in January after Buhari shook up the amnesty as much of the payments worth some $300 million annually had ended up in the pockets of “generals”. Some had become millionaires on contracts protecting pipelines they used to blow up.

The Avengers in August said they would halt hostilities to pursue talks with the government. Asked by Reuters whether the NDA would take part in Tuesday’s talks, Agbinibo said it had given a mandate to local community leader Edwin Clark to handle negotiations.

In an email written in patchy English, Agbinibo said the NDA was ready to talk but Buhari, a Muslim from the north, needed to end what it called discrimination against the Christian region where many complain they remain poor despite the area producing most of Nigeria’s oil.

Agbinibo did not make any specific demands, repeating only grievances widespread in the south that a clique of northerners was exploiting the oil wealth.

“Gone are the days, where successive governments will be killing our people and bombarding our communities under the cover of military programs to protect the oil industry without our interest,” the militant spokesman said.

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