In a new video released last night, Abubakar Shekau dashed hopes for a prisoner exchange to get the girls released.
"The issue of the girls is long forgotten because I have long ago married them off," he said, laughing.
"In this war, there is no going back," he said in the video received by The Associated Press in the same way as previous messages.
Nigeria's chief of defense staff, Air Chief Marshal Alex Badeh, on Oct. 17 announced that Boko Haram had agreed to an immediate cease-fire to end a 5-year-old insurgency that has killed thousands of people and driven hundreds of thousands from their homes in northeast Nigeria.
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Shekau in August announced that Boko Haram wanted to establish an Islamic caliphate, along the lines of the IS group in Syria and Iraq.
Fleeing residents have reported that hundreds of people are being detained for infractions of the extremists' version of strict Shariah law in several towns and villages under their control.
Boko Haram's kidnapping of 276 schoolgirls taking exams at a boarding school in the remote northeastern town of Chibok in April prompted an international campaign for their release and criticism of Nigeria's government for not acting quickly to free them. Dozens of the girls escaped on their own in the first couple of days, but 219 remain missing.
The government had said it had negotiated with two Boko Haram leaders in Chad, with talks hosted by President Idriss Deby, and that it was confident the girls would be freed soon. But Boko Haram has many factions.
Shekau's announcement further discredits the government of President Goodluck Jonathan, who on Thursday formally announced his candidacy for elections on February 14, 2015 in Africa's most populous nation.
Nigeria, with some 160 million people, is divided almost equally between Muslims who dominate the north and Christians in the south. The West African nation is the biggest oil producer on the continent and has its biggest economy.