UPDATE 1315 GMT: Pro-Assad bombing is continuing on opposition-held northwest Syria for a third straight day, mainly by regime helicopters:

Reports are circulating of a barrel bomb detonating inside a regime helicopter base in Hama Province, causing numerous casualties. Accounts vary on whether the cause was a bomb which exploded inside a helicopter preparing to take off, a helicopter crash, or a rebel rocket attack.

Russia and the Assad regime have continued their escalation of airstrikes and shelling on opposition-held Idlib Province in northwest Syria — possibly in preparation for a ground offensive, possibly in frustration that Turkey has blocked that offensive so far.

Residents and White Helmets rescuers reported the strikes across Idlib and northern Hama Province for the second day in a row. The area, along with western Aleppo Province, is the last major opposition territory in Syria.

The regime’s helicopters used barrel bombs on a string of villages and on medical facilities, a primary target — as in previous pro-Assad offensives such as east Aleppo city in 2016 and East Ghouta near Damascus this past spring — for Russian and regime warplanes.

A resident said that the village of al-Habeet alone was attacked by more than 15 helicopters, with at least two children killed and nine injured in strikes. Photos have been posted of slain infants.

“We pulled children out of the rubble. Where is the world to speak out against these crimes?” Abullah Qasem said.

At least another five people were killed in Qalat al-Madiq in northern Hama by artillery shelling, and Russia bombed Kafrzita and Latamineh, including the hospital in the latter town.

White Helmets spokesman Ahmad al-Sheikho said airstrikes and artillery shells have killed 24 civilians since late last week.

Three hospitals, two White Helmets civil defense centres, and an ambulance system have now been damaged in recent days, according to the Union of Medical Care & Relief Organizations.

Russia and Iran, the two essential backers of the Assad regime, failed last week to persuade Turkey to accept the assault to overrun Idlib and northern Hama.

The three countries declared a “de-escalation zone” last year, but Russia has broken the zones — using the pretext of eliminating “terrorists” — to enable the pro-Assad reoccupations in areas such as East Ghouta and much of southern Syria this spring and summer.

Russia and the Assad regime face a different challenge in the northwest because the Turkish military has been alongside rebels since August 2016, pushing out the Islamic State and then taking much of the Kurdish canton of Afrin.

See Syria Daily, Sept 8: Russia & Iran Split from Turkey in Summit Over Idlib