But warplanes struck the town of Khan Touman, southwest of Aleppo, the British-based Syrian Observatory for Human Rights said. Rebels also fought government forces east of Damascus, and jets struck the rebel-held towns of Maarat al-Numan and Idlib.
A recent surge in bloodshed in Aleppo, Syria's largest city before the war, wrecked the 10-week-old, partial truce sponsored by Washington and Moscow which had allowed U.N.-brokered peace talks to convene in Geneva.
The talks, attended by government and opposition delegates including representatives from rebel groups, broke up last month with both sides accusing the other of killing the truce.
Russia and the United States said in a joint statement they would step up efforts to convince the warring parties to abide by the ceasefire agreement.
"We have decided to reconfirm our commitment to the (ceasefire) in Syria and to intensify efforts to ensure its nation-wide implementation," they said.
"We demand that parties cease any indiscriminate attacks on civilians, including civilian infrastructure and medical facilities."
STRATEGIC PRIZE
Russia's military intervention last September helped President Bashar al-Assad reverse some rebel gains in the west of the country, including in Aleppo province.
But insurgents captured the town of Khan Touman last week, inflicting a rare setback on government forces and allied Iranian troops who suffered heavy losses in the fighting. Several Iranian soldiers were captured in the clashes, a senior Iranian lawmaker said on Monday.
Aleppo city is one of the biggest strategic prizes in a war now in its sixth year, and has been divided into government and rebel-held zones through much of the conflict.
The Observatory said warplanes struck rebel-held areas of the city early on Monday, and rebels fired shells into government-held neighborhoods.
Al Manar, the television channel of Damascus's Lebanese ally Hezbollah, said on Monday troops had destroyed a tank belonging to insurgents and killed some of its occupants.
On the eastern edge of Damascus, government forces and their allies shelled rebel-held areas and clashed with insurgents in the area, the Observatory and the rebel force Jaish al-Islam said. Three people were killed and 13 wounded in air strikes on Idlib, it said.
Jaish al-Islam agreed with a rival rebel group, Failaq al Rahman, that both would vacate a town they have been fiercely fighting over for almost two weeks, the Observatory said.
The groups, two of the strongest operating in the area, agreed to make no more attempts to militarily occupy the town of Misraba in the Eastern Ghouta suburb of Damascus, and return it to civilian rule. Quiet returned to the town after 13 days of heavy artillery exchanges which saw Jaish al Islam take control of it over the weekend and capture around 50 rival fighters.
Saudi Arabia condemned air strikes on a camp for displaced Syrians west of Aleppo last week which killed at least 28 people, saying it was part of "the genocide committed by Bashar al-Assad's forces against civilians in Syria".
A Saudi cabinet statement on Monday said the strikes on the camp, alongside the prevention of humanitarian aid deliveries to Syrians, constituted war crimes. Damascus has denied targeting the camp or obstructing aid deliveries.
French Foreign Minister Jean-Marc Ayrault, hosting a meeting in Paris of Assad's opponents, said Syrian government forces and their allies had bombarded hospitals and refugee camps.
"It is not Daesh (Islamic State) that is being attacked in Aleppo, it is the moderate opposition," Ayrault said.
The U.S.-Russian joint statement said Moscow would work with Syrian authorities "to minimize aviation operations over areas that are predominantly inhabited by civilians or parties to the cessation".
It also said the two powers would press the rival parties to the conflict to ensure humanitarian deliveries to several towns which have been largely cut off by the fighting.
Ayrault said Monday's meeting would call on Russia to put pressure on Assad to stop the attacks, adding that humanitarian aid must be allowed to reach those in need.
"Talks must resume, negotiations are the only solution," he said on radio RTL, ahead of his meeting with ministers from the United States, Saudi Arabia, Qatar, United Arab Emirates, Turkey and Britain, as well as Riad Hijab, chief coordinator of the main Syrian opposition negotiating group.
The joint statement issued by Washington and Moscow must be implemented, Ayrault said.