(Reuters) - Jihadist insurgents launched attacks against Syrian army posts in northwestern Syria on Sunday, which they said killed at least 25 soldiers and injured others to avenge civilian casualties during a recent escalation of army shelling.

Rebels of the Turkey-backed mainstream Free Syrian Army (FSA) factions told Reuters that dozens of insurgents belonging to the jihadist Ansar al-Tawheed group attacked two major army checkpoints near the village of Masasneh in northern Hama province in a dawn attack.

The army said in a statement that “a number of” its soldiers had been killed in attacks by “terrorists” and that bad weather had made the attacks easier.

Syrian state television showed several corpses, which Ansar al-Tawheed rebels said were the bodies of their suicide squads who had caught army troops off guard in an area close to opposition-held territory.

Stepped up missile and rocket strikes on villages and towns in northern Hama and adjoining Idlib province have been blamed by residents for dozens of civilian deaths and injuries since the latest army campaign began early last month.

The recent escalation has targeted schools, mosques and bakeries and caused widespread damage to infrastructure, civil defense workers and hospital sources in opposition areas say.

The army said a number of its fighters had been killed and injured and it sent a warning to the insurgents whom it said “persisted” in violating the agreement on a buffer zone brokered last year by Syria’s main battlefield ally Russia, and Turkey.”We will not idly stand by,” the army said in its statement quoted by state TV.

The Syrian foreign ministry issued a statement saying that the army was on “high readiness to repel such crimes and violations.”

Last September’s Sochi agreement staved off a Russian backed-assault on Idlib province, the last remaining opposition bastion, and now home to over 3 million people.

Russian Foreign Minister Sergei Lavrov was quoted by TASS news agency on Sunday as telling Turkey to live up to its commitments under the Sochi accord which requires banned jihadist groups to be expelled from a frontline buffer zone.

Lavrov said extremists who used to belong to the Nusra Front, Syria’s former chapter of al Qaeda, were in control of large swathes of territory in Idlib province and were expanding their hold.

Both civilian-run opposition bodies and residents say the strikes have prompted thousands to flee from a number of frontline villages and towns and have threatened a new exodus toward the Turkish border.

Khan Sheikhoun, which has borne the brunt of the recent rocket and missile attacks, has become a ghost town as most of its inhabitants fled to the safety of makeshift camps housing tens of thousands of people displaced after previous Russian and Syrian army air strikes.