Syrian guns pounded rebel positions in Aleppo and heavy fighting rocked the Old City amid a flurry of diplomatic activity, as world powers pressed on with the formidable task of seeking an end to the bloodshed.
Syrian troops battled rebel fighters near the international airport at Aleppo early on Wednesday, a watchdog said, adding that two children were killed in shelling in the central province of Hama.
The fighting erupted at dawn in the Nayrab area, around five kilometres (three miles) from the northern city's airport, which remained full operational, according to the Syrian Observatory for Human Rights.
Overnight, the army pounded rebel positions across Aleppo, focused on the southern districts of Bustan al-Qasr, Sukari and Kellaseh and the northeast districts of Sakhur, Shaar and Hanano, the Britain-based watchdog added.
Elsewhere in the country, a boy and a girl were killed and dozens of civilians were wounded when the army shelled the rebel village of Latamneh in Hama province, said the Observatory, which gathers its information from a wide network of activists on the ground.
The Syrian Observatory for Human Rights reported that five people, including a child were killed, in shelling of the rebel stronghold of Sakhur, and 12 people killed altogether in Aleppo province.
In the capital, meanwhile, an explosion rocked the upscale western district of Mazzeh overnight, and pro-regime gunmen fought rebels in Barzeh, another wealthy neighbourhood, the Observatory said.
Fierce clashes broke out south of the capital in Tadamun and the nearby Yarmuk Palestinian refugee camp, the watchdog said, adding that three civilians were killed in shelling of the area of Al-Hajar Al-Aswad nearby.
Just south of Damascus, at least one man was killed by sniper fire as clashes raged in the towns of Babila and Yalda, where the army launched a large-scale operation, the Observatory said.
At least nine people, including a woman and child, were killed in shelling of houses in the town of Kfar Zeita in the central province of Hama, according to the Observatory.
In Deir Ezzor province in the east, warplanes bombarded the town of Albu Kamal on the Iraqi border, killing four people, including three women. They also hit several districts of Deir Ezzor city, where clashes broke out and rebels deployed anti-aircraft guns.
The watchdog gave a toll of at least 85 people killed nationwide on Tuesday, most of them civilians, after a day in which nearly 140 lives were claimed.
More than 27,000 people have been killed since the revolt against President Bashar al-Assad broke out in May 2011, according to the Observatory.
International peace envoy Lakhdar Brahimi was in Cairo to meet exiled opposition leaders ahead of a planned visit to Damascus, his spokesman said. British Foreign Secretary William Hague was also there for talks with President Mohamed Morsi, amid a diplomatic flurry in the Egyptian capital, where Syrian neighbours gathered to discuss the conflict.
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UN chief Ban Ki-moon said Brahimi will meet Assad in Syria as he insisted that "the violence must stop by both sides".
He told reporters in Bern that he understood the frustration felt by many in the face of the UN Security Council's apparent paralysis in dealing with the spiralling crisis.
But "while we may be frustrated and troubled by not being able to address the situation in Syria, which has reached intolerable circumstances", he said.
"We should not be overly pessimistic about the strength and the commitment of the international community, especially the international organisations.
"Those countries who might have influence over two parties should exercise" that influence and should work towards "a political resolution reflecting the genuine aspirations of the Syrian people," he added.
Brahimi's spokesman Ahmad Fawzi said the envoy will meet "other officials, officials from the opposition as well as representatives of civil society" in Syria.
Pro-government newspaper Al-Watan, quoting a "private" source, said Brahimi would go to Damascus on Saturday.
A day after nearly 140 people were reportedly killed across Syria, the UN refugee agency said the number of civilians fleeing nearly 18 months of violence has reached more than 250,000.
UNHCR spokesman Adrian Edwards told reporters the humanitarian problems sparked by the conflict is "our biggest crisis."
"The complexity of the crisis is one of the aspects which sets it apart and the speed with which people have fled Syria," Edwards said.
The plight of the refugees was also under the spotlight as Oscar-winning actress Angelina Jolie spoke to journalists at the UN-run Zaatari camp in northern Jordan, flanked by UN High Commissioner for Refugees Antonio Guterres.
"We encourage the international community to do everything they can to support these refugees, and there is much to be done," said Jolie, a special envoy of the agency.
"It has been a very heavy experience," she said of her tour of the camp.
Syria's neighbours who have sheltered refugees have been pleading for funds and Jordan says it needs $700 million in international aid to cope with the influx.
The United Nations says more than 1.2 million civilians, more than half of them children, have also been displaced inside Syria.