Attacks on pipelines in Nigeria over the weekend have since then cost Africa's biggest economy around 470 million naira ($2.4 million) per day in lost gas and electricity, the government said on Thursday.
Reuters reports that the sabotage in the southern oil-producing Niger Delta, for which the former militant group in the region denied responsibility, followed years of relative calm in that part of Africa's biggest crude producer.
A spate of attacks there on oil installations and kidnappings of expatriate workers were halted by a 2009 amnesty.
State oil company NNPC said on Wednesday it had closed two of its four refineries due to subsequent crude supply problems.
No one has claimed responsibility for the attacks, in which former members of the largely defunct Movement for the Emancipation of the Niger Delta (MEND) denied involvement.
"What happened was not carried out by ex-militants," former MEND commander "Ex-General Pastor" Reuben Wilson told journalists in the southern city of Yenagoa on Thursday.
Last week authorities issued an arrest warrant for MEND commander turned businessman Government Ekpemupolo, known as Tompolo, as part of a crackdown on corruption.
"Some people claim Tompolo did it but he has come out to clear himself. If he is involved in such things, he comes out to say it; he is not behind these recent attacks," said Wilson.
The Ministry of Power, Works and Housing said a sabotaged pipeline, which contributes to the Escravos Lagos Pipeline System, has led to a loss of 160 million standard cubic feet per day (mmscfd) of gas worth $400,000.
"This is in addition to losses (of $2 million) to be incurred daily from affected power generation," said spokesman Hakeem Bello.
Fears of renewed unrest in the Delta arose after Muhammadu Buhari, a Muslim northerner who beat Goodluck Jonathan, a southern Christian, in presidential elections in March 2015, said he would end the amnesty programme.
The scheme will however continue for at least another year.