A Russian plan for rebels to withdraw from the Syrian city of Aleppo has been rejected by a powerful jihadist group.
Jabhat Fateh al-Sham, known as al-Nusra Front until it broke formal ties with al-Qaeda in July, vowed to fight on.
Russia has proposed that fighters and civilians take advantage of an eight-hour "humanitarian pause" on Thursday to leave rebel-held eastern districts.
Last month, government forces encircled them and then launched an all-out assault backed by Russian air strikes.
Some 2,700 people have been killed or injured in the bombardment since then, according to the Syrian Observatory for Human Rights, a UK-based monitoring group.
On Tuesday, Russia's defence minister announced that air strikes on rebel-held Aleppo had been halted two days ahead of the planned "humanitarian pause".
Sergi Shoigu said this would help "guarantee" the safety of six corridors through which civilians and could leave, and sick and injured people could be evacuated. Rebel fighters will be able to leave with their weapons via two special corridors.
Mr Shoigu also announced that military experts from Russia and countries who support the opposition - including the US, Turkey and Qatar - would meet in Geneva on Wednesday to start work on separating "terrorists" from "moderate" rebels.
However, Syria's political opposition says that is a virtually impossible task, reports the BBC's James Longman in Beirut.
Mainstream rebel factions have also dismissed Russia's proposal as a gimmick, and Jabhat Fateh al-Sham's response echoed their concerns that the evacuation of eastern Aleppo would mean surrender, our correspondent says.
A Jabhat Fatah al-Sham statement sent to the BBC pointed to similar initiatives in the central city of Homs in 2014 and the Damascus suburb of Darayya in August, where evacuations took place after years of siege and bombardment by President Bashar al-Assad's forces.
It was "clear", the statement said, that Russia wanted to "cleanse" areas of Sunni Muslims - who form the majority in Syria and dominate the opposition to Mr Assad, a member of the Shia Alawite sect - and to "differentiate" between rebel factions in order to weaken them.
"We choose not to give up our people," the statement said. "We will not betray their blood and we will continue our jihad until we remove the regime and any plan against that is rejected."
The UN, which has designated Jabhat Fateh al-Sham a terrorist organisation, says there are no more than 900 fighters from the group inside Aleppo, out of a maximum of 8,000 rebels in total.
In a separate development on Wednesday, officials in the besieged Damascus suburb of Muadhamiya said hundreds of people, many of them fighters, were being evacuated to the northern province of Idlib as part of a deal struck with the government last month that would see it retaking control.