BEIRUT - A jihadist offensive in a region of northwestern Syria where a safe zone deal had brought months of calm prompted heavy government and Russian air strikes Tuesday, including on a hospital, a monitor said.
Idlib province and some adjacent areas form one of four so-called de-escalation zones agreed in May by rebel backer Turkey and government allies Russia and Iran.
Front lines across the province had been relatively quiet since then but intense fighting erupted on Tuesday, the Syrian Observatory for Human Rights said.
Jihadist factions led by a former Al-Qaeda affiliate, which are not included in the de-escalation deal, launched a fierce assault on a string of government-held villages along the border between Idlib and neighbouring Hama province.
"An hour later, the regime launched air strikes on the operation's supply lines. Raids are now ongoing across southern Idlib province and northern parts of Hama province," said Observatory head Rami Abdel Rahman, adding that Russian warplanes later joined in.
Syrian raids hit a maternity hospital in the village of Al-Tah and a medical outpost in the town of Khan Sheikhun, as well as near two other hospitals in Idlib province, Abdel Rahman said.
"The raids on the maternity hospital in Al-Tah killed an elderly woman who was an employee of the hospital, in the first civilian death in air strikes in Idlib province since May," he added.
"The attack and air strikes are the most intense in the area since the de-escalation zone was announced in May," Abdel Rahman said.
According to the medical charity UOSSM, which has provided equipment to the maternity hospital, the woman killed was a cleaner in the facility and other medical staff were wounded.
In a statement distributed to journalists, the charity said two sets of strikes hit the maternity hospital, setting fuel storage tanks on fire and leaving its incubator room "totally destroyed."
UOSSM slammed the strikes and warned that "systematic attacks on hospitals are back despite de-escalation deals."
The clashes have killed at least 19 government troops and militia, the Observatory said. Twelve jihadists and two medics who had been working with them also died.
State news agency SANA also reported heavy clashes and said that government warplanes had hit the opposing forces' supply lines.
The fighting comes just days after Iran, Russia and Turkey announced they would jointly police the safe zone in Idlib and parts of adjacent Hama and Latakia provinces.
Russia has already deployed military police to the other three safe zones -- Eastern Ghouta near Damascus, parts of the south and some areas of the central province of Homs.
The de-escalation agreement excludes the jihadists of the Islamic State group and Hayat Tahrir al-Sham, an alliance dominated by Al-Qaeda's former Syrian affiliate.