BEIRUT: Deadly air strikes slammed into the last opposition-held town in Syria's Eastern Ghouta on Friday, killing 32 civilians in the first bombardment since talks sputtered over a rebel withdrawal.

Backed by Russia, Syrian troops had captured nearly all of the one-time opposition stronghold of Ghouta with a combination of ferocious bombing raids and negotiated withdrawals.

The Syrian Observatory for Human Rights said dozens of air strikes hit various parts of Douma, including some suspected to have been carried out by Russian warplanes.

"At least 32 civilians died, including seven children," said Observatory head Rami Abdel Rahman, adding that around 50 people were wounded.

A medic inside Douma described to AFP a state of chaos at the local hospital as wounded and dead were being brought in.

"The hospital is in a state of panic," the medic said.

"Dentists are carrying out emergency surgeries. Dead bodies are being brought in pieces and are unrecognisable."

State news agency SANA said Syrian air strikes hit the town on Friday in response to deadly rebel mortar fire from Douma.

It said mortar shells hit several suburbs of the capital and killed at least one person and wounded more than a dozen.

The regime and its ally Russia launched a blistering air and ground offensive on Eastern Ghouta in mid-February, killing more than 1,600 civilians and causing an international outcry.

The enclave on the eastern edge of Damascus had escaped government control since 2012 and, although it had shrunk over the years, it still covered sizeable territory two months ago.

The daily air raids kept residents cowering in basements for weeks and a ground assault soon sliced the area into three isolated pockets, each held by different rebel factions.