Damascus resumed air strikes on northwest Syria's Idlib Monday, a war monitor said, scrapping a ceasefire for the jihadist-run bastion and accusing its opponents of targeting an airbase of ally Russia.
The northwestern region of some three million people is one of the last major centres of resistance to President Bashar al-Assad's regime after eight years of war.
Damascus on Thursday said it had agreed to a truce from Friday to halt three months of deadly regime and Russian bombardment on the area that has killed more than 790 civilians.
But jihadists running the region on Saturday refused to comply with a key condition to that truce, declaring they would never withdraw from a planned buffer zone around the area.
Syria's army on Monday said it would resume operations against the region, accusing fighters inside of launching a flurry of rockets on the Hmeimim air base west of the bastion, causing "great human and material losses" nearby.
The Russian defence ministry said there had been no casualties on the base itself, but that, according to information from Syrian security services, rockets fell on a nearby district, "wounding four residents".
Syria's military said "armed terrorist groups, backed by Turkey, refused to abide by the ceasefire and launched many attacks on civilians in surrounding areas", according to a statement carried by state news agency SANA.
"The armed forces will resume their military operations against terrorists," it said, ending the truce that came into effect on Friday.
The Syrian Observatory for Human Rights, a Britain-based war monitor relying on sources inside Syria, said air strikes resumed on the bastion minutes after the truce was cancelled.
"Regime warplanes launched their first air strikes on the town of Khan Sheikhun in Idlib's southern countryside" since late Thursday, the Observatory said.
Experts and residents had been sceptical that the truce would hold, citing several previous failed ceasefires.
- We will 'never withdraw' -
Hayat Tahrir al-Sham, a jihadist group led by Syria's former Al-Qaeda affiliate, has since January controlled most of Idlib province as well as adjacent parts of the Hama, Aleppo and Latakia governorates.
But other rebels and jihadists are also present in the area.
The Idlib region is supposed to be protected from a massive government offensive by a Turkish-Russian deal struck in September last year in the Russian resort of Sochi.
But that deal was never fully implemented as jihadists refused to withdraw from the planned demilitarised zone around the bastion, which had been meant to separate them from regime forces.
On Saturday, HTS leader Abu Mohamed al-Jolani said his fighters would "never withdraw from the zone".
Just a day earlier, his group had warned it would respond to any ceasefire violations by its enemies.
While regime and Russian air strikes on the region had stopped from Friday, regime forces and jihadists traded artillery fire in various parts of the region.
On Sunday, regime rocket fire killed one woman in the Bidama district of Idlib province, according to the Observatory.
On Friday, a civilian was killed and three others wounded in jihadist rocket fire near Qardaha -- the ancestral village of President Bashar al-Assad -- in Latakia, SANA said.
Humanitarian groups have repeatedly raised the alarm in recent months over Russian and regime bombardment of Idlib, fearing one of the worst disasters of Syria's eight-year war.
The conflict has killed more than 370,000 people and displaced millions at home and abroad since starting with the repression of anti-Assad protests in 2011.
The Damascus regime is in control of around 60 percent of the country, after a string of victories against rebels and jihadists with major Russian military backing since 2015, but several areas remain beyond its reach.
These include Idlib, nearby territory held by Turkey-backed rebels, and a large swathe of the country's oil-rich northeast held by US-backed Kurds.
Agence France Presse