Syrian troops backed by artillery and warplanes fought rebels on multiple fronts Wednesday as peace envoy Lakhdar Brahimi described the death toll as "staggering" and destruction "catastrophic."
In the diplomatic arena, President Bashar al-Assad came under renewed fire from Turkish Prime Minister Recep Tayyip Erdogan, who said Syria had become a "terrorist state", and from Egyptian President Mohamed Morsi, who told him to go.
The Syrian Observatory for Human Rights said fighter jets bombed rebel zones in the northern city of Aleppo before dawn while ground troops simultaneously unleashed a barrage of shells.
After the bombardment, the bodies of at least 19 people were found, among them seven children, the Britain-based watchdog said.
Aleppo has been the target of a five-week-old offensive by regime forces trying to dislodge rebels who took over swathes of the country's commercial capital in July.
Activists have reported relentless bombardments and food shortages in those neighbourhoods still held by rebels, while an AFP reporter who was in Aleppo on Tuesday said life in the loyalist-controlled central area was relatively normal.
Rebels meanwhile on Wednesday attacked Hamdan military airport near Albu Kamal town in the eastern province of Deir Ezzor, the Syrian Observatory said.
Having failed to persuade the international community to impose a no-fly zone over the country, the rebel Free Syrian Army has increasingly targeted airports used by regime attack helicopters and warplanes.
"Fighting has been going on for hours inside Hamdan airport between soldiers and rebels, who have taken over large sections of the site," Observatory director Rami Abdel Rahman told AFP, adding that at least six rebels died in the assault.
In Deir Ezzor city, two people were killed, one of them by sniper fire, the Observatory said.
Several blasts were heard in the Jubar district of the capital Damascus as it came under heavy bombardment, and explosions were also heard in the Yalda area just south of the city, the watchdog said.
In the central city of Homs, the rebel bastion of Khaldiyeh came under fierce mortar fire, and three children were killed in bombardment by regime forces of the Ariha area in Homs province, it added.
-- 'Staggering' death toll --
Brahimi, the newly appointed UN-Arab League peace envoy for Syria, said on Tuesday the death toll in the country was "staggering" and the destruction "catastrophic."
The Algerian former foreign minister, who took up his post on Saturday, also warned that the situation across Syria was "deteriorating steadily."
Turkey's Erdogan, who turned against Assad when the Syrian president resorted to brutal force against unarmed protesters, used his strongest language yet against his erstwhile ally.
"The regime in Syria has become a terrorist state," Erdogan told his ruling AKP meeting in Ankara. "Syria is not an ordinary country to us. We do not have the luxury to remain indifferent to what's happening there."
Assad also came under fresh attack from Egypt's Morsi, who told a meeting of Arab League ministers in Cairo that it was time for the Syrian regime to step down.
"I tell the Syrian regime 'there is still a chance to end the bloodshed'. Now is the time for change... no time to be wasted talking about reform," Morsi said.
He urged Assad to "take lessons from recent history" and step aside, in reference to Arab Spring revolts that overthrew the longtime dictators of Tunisia, Egypt and Libya.
Morsi, who last week slammed the Syrian regime as "oppressive", stressed that a resolution of the crisis was the responsibility of Arabs.
"The Syrian blood that is being shed day and night, we are responsible for this," Morsi said. "We cannot sleep while Syrian blood is being shed."
Less stridently, China said on Wednesday it supported a political transition in Syria and defended its record during a visit by US Secretary of State Hillary Clinton.
Clinton, meeting in Beijing with China's top leadership, reiterated she was "disappointed" by Chinese and Russian vetoes of UN resolutions that would have threatened action against Assad to end the spiralling bloodshed.
Chinese Foreign Minister Yang Jiechi called for all sides to end fighting, telling a joint news conference with Clinton: "Let me emphasise that China is not partial to any individual or any party."
In a preliminary toll, the Observatory said at least 34 people were killed nationwide on Wednesday -- 28 civilians and six rebels.
The watchdog, which relies on information from a network of activists on the ground, says more than 26,000 people have been killed overall in Syria since the revolt against Assad's rule broke out in March 2011.
The United Nations says about 20,000 have died.