Government warplanes and helicopters struck rebels Tuesday as they struggled to advance near Syria's two main cities, Damascus and Aleppo, a monitoring group said.
In other developments, shelling by both loyalists and rebels killed civilians across the country, including in the capital.
"Helicopters fired explosives-laden barrels at Muban... near the town of Sfeira in the east of Aleppo province," which is a strategic flashpoint because the army has been fighting for months to secure its route into Aleppo city, said the Syrian Observatory for Human Rights.
Loyalist helicopter gunships also unleashed heavy gunfire on rebel positions near Kwayris military airport, which has been under rebel siege for months, said the Britain-based monitor.
In Aleppo city, warplanes carried out an air strike on the battered Bab Nairab neighbourhood, scene of a horrific regime missile strike in July that killed at least 29 people, mostly children.
As clashes raged on in Damascus's Jobar, Qabun and Barzeh neighbourhoods, the army pressed its bid to crush the rebels' positions on the city's outskirts.
Days after advancing rebels broke through near Mleiha, southeast of Damascus, the air force unleashed an air strike on the area, said the Observatory.
Mleiha is important because it lies near pro-regime areas in the capital, which the army is trying to secure from rebel attacks.
According to state news agency SANA, at least two people were killed in a shelling attack against Jaramana, a majority Christian-Druze neighbourhood in southeastern Damascus firmly under regime control.
The Observatory confirmed the attack, saying one of those killed was a child.
Violence also raged further south, with army shelling on Inkhil in Daraa province killing a man and a child from the same family, said the group.
In the central province of Homs, warplanes were deployed to strike rebels fighting troops in countryside areas that are important because they lie near the Lebanese border and just northeast of Damascus.