By Felix Onuah and Anamesere Igboeroteonwu
ABUJA/ONITSHA, Nigeria (Reuters) - Nigeria wants to talk with the Niger Delta Avengers militant group which has claimed a string of attacks that cut crude output sharply, its oil minister said, trying to stem a tide of violence in the country's main oil-producing region.
The southern Delta swamps, where many complain of poverty and oil spills, have been hit by militant attacks on oil and gas pipelines which have brought Nigeria's oil output to a 20-year low, and helped push oil prices to 2016 highs on Tuesday.
President Muhammadu Buhari had appointed a team led by the national security advisor "to begin the process of a very intensive dialogue with those caught in the middle of this," Oil Minister Emmanuel Ibe Kachikwu said late on Monday, while Buhari was in Britain seeking medical treatment.
"I want to call on the militants to sheath their weapons and embrace dialogue with government," he said. "We are making contacts with everybody who is involved, the ones that we can identify, through them, the ones that we can't identify so that there is a lot more inclusiveness in this dialogue."
"Probably we will suspend the operations of the military in the region for a week or two for individuals in the creeks to converge for the dialogue," he said.
There was no immediate response from the Avengers group which has been issuing statements through its Twitter account.
Vice President Yemi Osinbajo, who had been expected to travel to London to meet financial investors on Tuesday, met instead in Abuja Niger Delta state governors to discuss ways to end the militancy, an official said.
Adding to the trouble of authorities trying to stem the violence, a group in the southeast calling for secession declared support for the Avengers.
"We support the Niger Delta Avengers," said Uche Madu, a spokesman for the Movement for the Actualization of the Sovereign State of Biafra (Massob) which wants secession for the region which already fought a 1967-70 civil war.
A former militant group, the Movement for the Emancipation of the Niger Delta, which laid down arms in 2009 under a government amnesty, accused the army of a "disproportionate use of force".
MEND, which was one of the largest militant groups, also said the Delta Avengers had attracted some of its former fighters. So far it has been unclear who is behind the Avengers.
"Many of whom were MEND commanders and fighters who jumped on the Presidential Amnesty gravy train without knowing why they took up arms in the first place," the MEND statement said.
Kachikwu also said Nigeria's oil output was between 1.5 million and 1.6 million barrels a day, down from 2.2 million barrels at the start of the year.
"Over the last two months, we have probably lost about 600,000 barrels from various attacks of militants in the area," he said.
The U.S. embassy in Abuja said in a statement it was concerned about the violence in the Delta, urging "all parties to resolve their disputes through peaceful means."
(Reporting by Felix Onuah, Ulf Laessing, Camillus Eboh and Tife Owolabi and Anamesere Igboeroteonwu; Writing by Ulf Laessing, editing by Louise Heavens and William Hardy)