The army said it was opening eight corridors to provide safe passage for those leaving but the ceasefire suffered an early blow.
The army said it was opening eight corridors to provide safe passage for those leaving but the unilateral ceasefire suffered an early blow when clashes broke out at one of them, an AFP correspondent said.
Artillery exchanges erupted around the crossing point on the front line in the city centre, the photographer said. The state SANA news agency blamed "terrorist groups".
More than 250,000 civilians have been trapped in the rebel-held east of the city under near-continuous siege since mid-July and under devastating bombardment by Russian and Syrian government aircraft which only halted on Tuesday.
Russia has said the pause in a Syrian army offensive launched on September 22 will continue until at least 1600 GMT and could be extended. The Syrian army has said it will last three days.
Syrian and Russian warplanes already halted strikes on rebel districts from 0700 GMT on Tuesday.
The Syrian army has said it is opening eight corridors for civilians to leave, two of which can also be used by rebel fighters provided they leave behind their weapons.
Residents interviewed by AFP said they were eager to leave but wanted more reassurance they would be safe.
"Even though I need to leave because of the deteriorating living conditions caused by the siege and the lack of food or work, I don't want to risk my life or my family's by being among the first to leave," said Mohammed Shayah, an unemployed father of four.
The United Nations has said the duration of the pause is not long enough to provide any relief supplies.
UN envoy Staffan de Mistura said the truce would be long enough to safely evacuate just 200 wounded.
More than 2,000 people have been wounded since the army launched its offensive, according to the United Nations. Some 400 have been killed.
The civilian casualty toll has drawn international condemnation with Washington saying the bombardment could amount to a war crime.
Moscow has dismissed the accusation saying that it is propaganda that ignores the reality of the presence of jihadist fighters blacklisted by the United Nations in rebel areas.
It has repeatedly demanded that fighters of other rebel groups break ranks with those of former Al-Qaeda affiliate, the Fateh al-Sham Front.
The United Nations has urged the group's fighters to leave Aleppo and its envoy even offered to accompany them.
But both the jihadists and other rebels have insisted they will fight on.
Russian President Vladimir Putin held tough talks with the French and German leaders in Berlin on Wednesday about the crisis after which he raised the possibility of extending the unilateral ceasefire.
French President Francois Hollande condemned the bombing of the city as "a war crime." German Chancellor Angela Merkel described it as "inhumane and cruel".
Syria analyst Thomas Pierret, of the University of Edinburgh, said the halt in Russian air strikes was about Moscow "managing international pressure".
"Russia is periodically trying to mitigate tensions with the West on Aleppo through such initiatives. This is the continuation of war by diplomatic means," he said.
Five years of efforts to put an end to the conflict in Syria have all failed, but over the past week world powers have made new efforts to broker a lasting truce.
Besides the Berlin summit, talks were held on Wednesday in Geneva between Russian and US officials and representatives of key rebel backers Qatar, Saudi Arabia and Turkey on distancing other opposition groups from the jihadists.