The main rebel coalition in Chad, the Union of Resistance Forces (UFR), said Thursday it was resuming its fight against President Idriss Deby Itno's regime.
"We have decided to resume the struggle. An armed struggle, of course," Timan Erdimi, a key leader of the group, told AFP from Qatar, where he is in exile.
The UFR had laid down its weapons after a 2009 peace deal between Chad and Sudan, which normalised relations after years of accusations that each country was supporting rebels in the other.
But Erdimi said his group had been excluded from the peace negotiations.
"When the accord with Sudan was signed, there should have been discussion with us, but we've been in Doha for two years and eight months now and we've seen nothing of the sort," he said.
"Deby thought that because of the accord he could get by with doing nothing. We've never trusted Deby. We didn't give up all our weapons, we still have some hidden. Of course we're not at 100 percent, but we will make it up on the ground as usual."
Erdimi, who is the president's nephew, was part of Deby's inner circle and once served as his uncle's chief of staff before falling out with him and jumping ship to join the rebellion.
He went on to help lead a series of failed attacks targeting the Deby regime, including one in 2008 in which rebels stormed the capital N'Djamena in a bid to oust the president.
The insurgents reached the gates of the presidential palace in February 2008. But the tide turned when France, formerly Chad's colonial ruler, provided key intelligence and ammunition to government forces, who then managed to beat back the divided rebellion.
Erdimi led the Rally of Forces for Change (RFC), one of the main rebel groups in the country, and became the chief of the UFR when it was founded in 2009.
But another rebel leader, Mahamat Nouri, later pulled out of the UFR coalition and founded a rival group.
Erdimi said Thursday he was now seeking to unite the divided anti-Deby rebellion.
"The door's open to everyone," he said. "Nouri can also come."
He said rebel forces were "arriving from everywhere", with commanders taking up positions on the border between Chad and Sudan.
But he said he did not necessarily plan to return to Chad to lead the fight.
"Me being on the ground in Chad isn't essential," he said.
Chad's Communication Minister Hassan Sylla Bakari said he was "unpleasantly surprised by the rags crawling out of the shadows to once again speak of war in Chad".
The minister told AFP that Erdimi "has no one behind him, he has been completely forgotten. No Chadian could enter into this logic. There is no Chadian rebellion, neither in Chad nor elsewhere. In Chad there is calm, peace and stability."