Beirut — Air strikes on Syria's rebel-controlled Douma killed eight civilians on Saturday, said the Syrian Observatory for Human Rights, as government forces resumed a military blitz of the town.

The Britain-based monitor said it could not confirm whether the strikes were carried out by Syrian government warplanes or those of its ally, Russia.

It was the second day of heavy bombardment on Douma, with at least 40 civilians killed on Friday in a sudden resumption of strikes after a more than week-long lull.

The renewed raids appear to be an attempt to pressure Jaish Al-Islam -- the Islamist group that holds the town -- to agree to the regime's terms of a withdrawal.

Six civilians were also killed and dozens more wounded as Douma rebels shelled the capital Damascus on Saturday, Syrian state media said.

More bombing raids slammed into the town on Saturday, the Britain-based Observatory and a civil defense worker said.

"The bombing still hasn't stopped. There are three warplanes in the sky and two helicopters," Firas Al-Doumi, a rescue worker inside Douma, told AFP on Saturday morning.

Syrian state television broadcast live footage of raids over Douma, showing billowing clouds of smoke over a devastated urban landscape.

Assad is keen to recapture Ghouta to eliminate the opposition from the outskirts of Damascus and end years of rocket fire on the capital.

Since February 18, the regime's offensive has killed more than 1,600 civilians and kept residents cowering in basements for weeks. A ground assault then sliced the area into three isolated pockets, each held by different rebel factions.

The first two were evacuated under Russian-brokered deals last month that saw more than 46,000 rebels and civilians bussed to opposition-held Idlib province in the northwest.

Tens of thousands also fled into government-controlled territory through safe passages opened by Russia and Syrian troops.

Moscow stepped in to negotiate a deal for Douma, the third and final pocket where Jaish al-Islam had been angling for a reconciliation agreement that would allow them to stay as a police force.

Following a preliminary accord announced by Russia on Sunday, nearly 3,000 fighters and civilians were evacuated from Douma to northern Syria.

But as talks dragged on, Syria and its Russian ally threatened Jaish Al-Islam with a renewed military assault if they did not agree to withdraw.

It remains unclear exactly why the talks fell apart this week.

SANA said they faltered when Jaish Al-Islam refused to release detainees they were holding in Douma, adding that the military assault would only stop if hostages are released.

Others have blamed internal rebel divisions over the withdrawal process.

Top Jaish Al-Islam political figure Mohammad Alloush on Friday blamed power struggles between the regime's allies.

"The talks were going well... Their only shared interests is the blood of civilians," he said.

The resumption of strikes stunned civilians.

"All of a sudden, with no warning, the shelling starts. There were 20 strikes in 15 minutes," Mohammed, a medic, told AFP from Douma on Friday.

The wounded were being brought in with fractures and other injuries, and there had been three amputations on Friday alone, he said.

Syrian troops also carried out a ground operation Friday in the orchards surrounding Douma.

On Saturday, fresh artillery fire hit those fields, said the Observatory.

"The regime is trying to tighten the noose around Douma from the west, east, and south," said Observatory head Rami Abdel Rahman. — Agencies