New UN-Arab League envoy denies saying it is too soon for President Assad to step down as clashes continue across Syria.
Two children were among at least 19 people reported killed in shelling by the Syrian army, as clashes with rebels continued on the first day of the Muslim Eid al-Fitr holiday.
Activists said the children were killed on Sunday during continued shelling on the town of Maaret al-Numan in Idlib province.
The violence came as Lakhdar Brahimi, the new UN-Arab League Joint Special Representative in Syria, denied making comments that that it was too soon for Bashar al-Assad, the Syrian president, to step down.
In other parts of the country, troops were also reported to have bombarded the besieged city of Rastan, in the central province of Homs, and the eastern city of Deir Ezzor.
Children across the Muslim world were set to receive new clothes and gifts for Eid,
but in Syria there was no respite from the bloodshed which the activists say has killed more than 23,000 people since March last year.
"There is no holiday," said Mohammed Radwan, 34, standing near an apartment building in Aleppo's Tariq al-Bab neighbourhood, which was hit by an airstrike the day before.
"The electricity comes and goes, the jets fire on us and no one has any work. All we'll do today is clean up the rocks and
clashes raged in the Saif al-Dawla and Izaa districts of the northern city of Aleppo, a key battleground of the conflict since rebels seized large swathes from July 20.
Fierce fighting continued to rage between rebel fighters and government forces for control of Aleppo's international airport, a strategic target for both sides.
Opposition forces said they were making gains in the city and were hopeful of capturing the airport, an important strategic target.
Brigadier General Mark Kimmitt, a former US state department military advisor, told Al Jazeera that the rebels have managed to persevere largely because of the nature of urban warfare.
"As we always see in urban terrain, the advantages that are held by a technologically superior military, such as the Syrian army, those advantages of aircraft, of tank, those are in many ways neutralised inside a city," said Kimmitt.
At least 137 people were killed across Syria on Saturday, including 63 civilians, 31 rebel fighters and 43 soldiers, the UK-based Syrian Observatory for Human Rights said.
'Last chance to stay alive'
Amid the violence, Syria's state-run TV aired footage of President Bashar al-Assad performing Eid prayers in a mosque in Damascus on Sunday.
It was his first appearance in public after a bombing in the Syrian capital last month that killed the country's defence minister and three other top security officials.
The last time Assad appeared in public was on July 4 when he gave a speech in parliament.
Assad's appearance comes amid much speculation on the whereabouts of Vice President Farouk al-Sharaa
, who was said by some members of the Free Syrian Army (FSA) to have defected to the opposition.
On Saturday, his office denied the reports and said Sharaa "did not think, at any moment, of leaving the country".
Sharaa did not appear in the footage at the mosque with Assad.
Meanwhile, Syrian helicopters dropped leaflets over Aleppo urging residents not to shelter rebels and warning the FSA it had one last chance to surrender.
Some of the leaflets dropped late Saturday, in what rebels and residents said was a first, were designed as official-looking checkpoints passes for supporters of the rebels wishing to surrender.
"The holder of this pass is allowed to cross security forces checkpoints to surrender. The holder of this pass will be well treated and reunited with his family after verifications are conducted," the leaflet read.
Other more basic leaflets printed on pink or white paper urged the rebels to put down their weapons.
"Your last chance to stay alive is to give up your weapons because there is nothing you can do against the Syrian army," read one leaflet, in part.
The AFP news agency reported that fighters in Aleppo had laughed off the leaflets and continued to fight, saying that their next step is to take the out two remaining airforce bases, a radar station, and the new army headquarters in the province of Aleppo.
The latest development came as the last 100 of 300 UN monitors who had been in the country prepared to leave Syria on Sunday.
UN monitors wind up mission in Syria
The UN observers' departure comes after the UN Security Council agreed to end the mission and support a small new liaison office that will support any future peace efforts.
In an interview with Al Jazeera on Sunday, veteran Algerian diplomat Brahimi said that for him, it was "too early to have a say" on whether Assad should step down.
"I could not talk about such a matter or any other matters unless I arrive in New York or Cairo to see what is the plan to be carried out," said Brahimi.
Brahimi had been quoted by news agencies on Saturday as saying that it was too soon for Assad to step down, something he denies saying.
Reports of the alleged comments had caused fury among Syrian dissidents and the opposition Syrian National Council (SNC) described the comments as "unacceptable".
"The revolutionary Syrian people were shocked and dismayed by Mr Lakhdar Brahimi's statements," the SNC said in a statement.
"We call on the international envoy - who has not yet consulted with any Syrians on his appointment or his mission - to apologise to our people for taking this unacceptable position," it added.
Brahimi told Al Jazeera that he has asked the SNC for an apology. "They should call and ask me to make sure if I said so," he said.