Intense fighting in the central Syrian city of Homs has left 60 to 70 percent of a besieged rebel-held district damaged, destroyed or uninhabitable, a monitoring group said on Sunday.
The estimate from the Syrian Observatory for Human Rights came nine days into an all-out assault by troops loyal to President Bashar al-Assad on the rebel-held Khaldiyeh and Old City neighbourhoods, which have been under siege for more than a year.
On Sunday, new air strikes, tank shelling and rocket fire hit the city, said the Observatory.
"Sixty to 70 percent of buildings in Khaldiyeh are either totally destroyed, partially destroyed, or unsuitable for habitation," Observatory director Rami Abdel Rahman told AFP.
Homs is Syria's third-largest city, and tens of thousands of its residents have fled the fighting.
"Of all Syria's cities, Homs has suffered the highest levels of destruction... Images of Homs make it look like a world war has hit the city," Abdel Rahman added.
Amateur video posted online by activists on Sunday showed flames and thick black smoke rising from several empty burnt-out buildings already riddled with holes.
Some structures shown in the video are barely standing.
"Even if the regime takes the neighbourhoods back, there's barely a house left standing to return to," said Abdel Rahman.
On Sunday, government troops used mortars, rocket fire and heavy artillery to target rebel areas in the city, the Britain-based Observatory said.
Signup to our newsletter and follow us on Facebook and Twitter!
"We're under heavy pressure, especially on the Khaldiyeh front. The fighting is fierce and we are living off very scarce supplies," said anti-regime activist Abu Khaled.
"We have run out of nearly all fuel and medical equipment after more than a year under siege," he told AFP via the Internet.
Regime forces have made slow progress, seizing several buildings on Khaldiyeh's edges in recent days, "tightening the siege" on the rebels, he added.
"Homs has important symbolic value for the revolution, and if the regime takes it over, it will score a big victory," he said.
Homs lies in central Syria, straddling supply routes to all the country's provinces.
According to the United Nations, some 2,500 to 4,000 people are trapped in the besieged areas of the city.
In Damascus, regime warplanes targeted Jubar in the east of the capital, while tanks hit Qaboon in the northeast, said the Observatory.
Several mortar rounds hit Yarmuk Palestinian refugee camp in southern Damascus, it added, as rebels and troops clashed nearby.
In northern Damascus, the army tried to storm Barzeh, where rebels are still holed up, the watchdog said.
Elsewhere, a blast hit a regime post in the heart of Aleppo, Syria's commercial capital, said the Observatory, without elaborating on casualties.
Syria's 27-month war has killed more than 100,000 people, the group estimates.
On Saturday alone, at least 69 people were killed nationwide, it said.