Fighting raged in a strategic district of Syria's commercial capital Aleppo on Saturday, the third day of a rebel offensive to seize the city, monitors said.
The United States and Britain, meanwhile, pledged more than $55 million more in funding for humanitarian aid and the civilian opposition.
The focal point of combat was Salaheddin, a rebel stronghold on the southwest side of the city where insurgents attacked an army position, the Syrian Observatory for Human Rights said.
It also reported that the wooden-doored shops of the famous souk marketplace in central Aleppo, a popular tourist destination before the violence erupted in March 2011, were set ablaze in the clashes between rebels and soldiers.
Elsewhere, the army stepped up operations in the eastern suburbs of Damascus.
"The rebels have a strong presence, and the army wants to root them out once and for all," Observatory head Rami Abdel Rahman said.
Damascus-based citizen journalist Matar Ismail said the "army is taking revenge against Damascus, and it is mainly the civilians who are paying the price.
"The situation here is very bad, especially in the eastern areas. And the regime is executing many men summarily."
The eastern suburbs of the capital are the centre of operations for the rebel Free Syrian Army's fiercest and best organised battalions, including Tajamo Ansar al-Islam.
On Wednesday, two car bombs struck an army headquarters in the heart of Damascus, and Tajamo Ansar al-Islam was the first FSA group to claim responsibility for the operation.
Meanwhile, fighting raged in several districts of Aleppo, where rebels launched on Thursday an all-out campaign to capture the northern city, the scene of some of Syria's fiercest violence since July 20, the Observatory said.
Battles broke out in the central Old City and eastern Arkub districts, the Britain-based watchdog said.
Residents of Suleiman al-Halabi, one of Aleppo's main districts, reported finding an unknown number of abandoned corpses on the streets, Abdel Rahman told AFP.
At least 72 people were killed in violence across the strife-torn country, including 31 civilians and 18 soldiers, said the Observatory. Among the dead was a year-old infant killed in shelling in the town of Maskana near Aleppo.
More than 30,000 people have died in 18 months of violence since the outbreak of the revolt against President Bashar al-Assad, the watchdog says.
-- $45 million in extra US funding --
In New York on Friday, US Secretary of State Hillary Clinton unveiled a total of $45 million (35 million euros) in new funding for humanitarian aid and to help Syria's civilian opposition.
Some $30 million would go towards aid, bumping up the total US funding for humanitarian relief to $130 million, with a further $15 million for the civilian opposition, she told a meeting of the Friends of Syria.
Washington has stuck by its refusal to provide arms and military support to the rebels, fearing it would further complicate the situation on the ground.
Clinton also attacked Iran's role in the conflict. "There is no longer any doubt that Iran will do whatever it takes to protect its proxy and crony in Damascus," she told the Friends of Syria meeting.
British Foreign Secretary William Hague, meanwhile, announced an extra £8 million ($12.9 million/10 million euros) in aid in addition to the £30.5 million already donated.
But in a speech to the UN General Assembly, Russian Foreign Minister Sergei Lavrov accused Western powers of obstructing an international solution to the crisis.
He insisted that Geneva accords adopted on June 30, which do not call for Assad to step down, should be the basis of any transition plan and charged that Western powers had rejected them.
Russia has been heavily criticised at this week's UN General Assembly by governments that accuse it of thwarting efforts to halt the civil war by using its veto powers to quash resolutions targeting the Damascus regime.
As the exodus of Syrians fleeing the fighting swelled, a Turkish official said a Saudi charity has agreed to build a container city that can house 10,000 refugees in Turkey's Kilis province near the border.
The project of the Saudi National Campaign to Support Brothers in Syria is expected to be ready within a month, and will be the second camp in Kilis, which already shelters 12,000 refugees, the official told AFP.