Syrian military says three-day ceasefire came into effect this morning
Clashes have broken out in an area designated as a "humanitarian corridor" for civilians to leave the besieged Syrian city of Aleppo.
Only hours earlier, the Syrian military announced it had begun a three-day unilateral ceasefire in the city to allow civilians and rebels to leave.
Syria's state news agency SANA blamed "terrorist groups" for breaking the so-called humanitarian pause, and there were artillery exchanges around the crossing point.
SANA said the army had opened eight exit corridors in two designated areas in northern Aleppo and state television showed green buses waiting to move people out.
Nearby, an army loudspeaker was heard blaring out: "We guarantee a safe exit, save your families.
"The battle for returning Aleppo to the nation's fold is in its last phases. There is no point in continuing the fight."
On Tuesday, Russian and Syrian forces halted air strikes on Aleppo ahead of the ceasefire.
But a powerful rebel jihadist group is refusing to leave the besieged eastern part of the city.
It has claimed the ceasefire is part of a psychological campaign to get the rebels to surrender.
In September, Syrian government forces encircled the rebel groups and with Russian support, launched an all-out assault.
Since then, around 2,700 people have been killed or injured in the bombardment, according to the UK-based monitoring group, the Syrian Observatory for Human Rights.
The air strikes on Aleppo could amount to war crimes, according to Western leaders.
German Chancellor Angela Merkel and French President Francois Hollande repeated the claim when they had talks with President Putin in Berlin on Wednesday.
A summit getting underway in Brussels is threatening sanctions against the Syrian regime.
Mr Hollande said the bombardment was "unacceptable, intolerable, unbearable", while Mrs Merkel described it as "horrific".
Russia has rejected the accusations, as has Syrian President Bashar al Assad.
He has also claimed that the photograph of a traumatised young boy covered in blood and dust which made headlines around the world is a fake.
He told Swiss television he had photographic proof that the images of five-year-old Omran Daqneesh, who was pictured following an air strike on Aleppo, were forged.
President Assad also said the current ceasefire was an important step, but was not enough.
He said civilians wanted to leave the city but "terrorists" won't let them.