Syria conflict: Russia extends Aleppo ceasefire by 24 hours
Russia says it will extend by 24 hours its "humanitarian pause" in air strikes on rebel-held eastern Aleppo, taking the break up until Friday afternoon.
Defence Minister Sergei Shoigu said President Vladimir Putin had ordered the extension to 16:00 (13:00 GMT).
UN humanitarian chief Jan Egeland said he hoped hundreds of sick and wounded could be evacuated by the deadline.
But rebels have rejected the truce, with reports of continued clashes and few residents heeding calls to leave.
Russian Foreign Minister Sergei Lavrov said militants were "preventing the evacuation of the population", as he discussed the crisis by phone with US Secretary of State John Kerry.
In a separate development on Thursday, Belgium demanded that Russia formally withdraw claims that two Belgian fighter jets had killed six civilians in air strikes on a Kurdish village in northern Syria on Tuesday.
On Wednesday Belgium summoned the Russian ambassador in Brussels to dismiss the accusations as "totally groundless".
Russia's military insisted that its radar backed the claim.
- Russia and the West: Are we entering a new cold war?
- Life under siege in rebel-held Aleppo
- Why Assad wants to take Aleppo
- Aleppo: Key battleground in Syria's war
Russian and Syrian government forces suspended their air strikes on Tuesday to pave the way for the truce, which is aimed at opening up eight exit corridors from the east of the city to allow residents to leave the besieged area.
Rebel fighters have been given a chance to leave via two corridors, provided they leave behind their weapons.
But soon after the truce took effect at 05:00 GMT on Thursday, some of the corridors reportedly came under fire, with opposition and government forces blaming each other.
Mr Egeland, who heads the UN humanitarian taskforce for Syria, said he hoped the first of "several hundred" people most in need of medical help could be brought out on Friday with the help of the World Health Organization and the Red Cross.
"We believe we now have all of the green lights that we need both from the Russians and the government and from the armed opposition groups," he said.
But the truce was reported to have had little impact on the ground. Ammar Jaber, a correspondent for Orient News, a Dubai-based pro-opposition TV channel, said he had seen just a few civilians leaving at two of the crossings intended for evacuation.
Mr Jaber said Syrian government forces were targeting the corridors with sniper and rocket fire.
Last month, Syrian government forces encircled the eastern section and launched an all-out assault backed by Russia.
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. About 250,000 civilians who live in Aleppo have been trapped by the fighting.
Western leaders have said Russian and Syrian air strikes on Aleppo could amount to war crimes, an accusation rejected by Russia.
Jihadist group Jabhat Fateh al-Sham, which was known as al-Nusra Front until it broke formal ties with al-Qaeda in July, has vowed to fight on despite Russia's pledge of a truce.
Mainstream rebel factions also dismissed Russia's proposal as a gimmick.
The UN, which regards Jabhat Fateh al-Sham as a terrorist organisation, says the group has 900 fighters inside Aleppo, out of a maximum of 8,000 rebels in total.