Nearly two dozen civilians have been killed just outside of Damascus in a Syrian government-led offensive targeting rebel-held areas, a war-monitor group said.

Air strikes on Eastern Ghouta, a suburb of the Syrian capital, killed at least 23 people on Monday, the UK-based Syrian Observatory for Human Rights reported.

The Observatory said at least 70 people were also wounded in the attacks, which the group said were carried out by Syrian forces and their Russian allies.

Of those killed, at least nine civilians, including two children, were killed in an air raid on a market in the town of Beit Sawa, while another six civilians, including one child, were killed in the town of Hazzeh, AFP news agency reported.

Syrian state media also said shelling on the Old City of Damascus, which is held by the government, killed one woman and wounded three other civilians.

Eastern Ghouta is the last remaining rebel-held stronghold near Damascus and has been under a government siege since 2013.

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Human rights groups have struggled to access the area to provide an estimated 400,000 residents with much-needed food and medicine.

Local hospitals are running out of medical supplies and an acute food shortage has led to severe malnutrition.

Late last month, Syrian activists accused President Bashar al-Assad's forces of violating a Russian-brokered ceasefire in the area.

The aerial bombardment of Eastern Ghouta came amid reports that at least 18 civilians were killed and dozens more were injured in a Syrian government bombardment on northern Idlib province, which is also held by rebel groups.

The International Committee of the Red Cross in Syria reported medical facilities were targeted in Idlib and the town of Hama.

Alarming news from #Syria. We’re receiving reports of multiple medical facilities targeted in #Hama and #Idleb. With the majority of hospitals no longer operating in these areas, these latest attacks will deprive tens of thousands of life-saving care.

#NotATarget — ICRC Syria (@ICRC_sy) February 5, 2018

"With the majority of hospitals no longer operating in these areas, these latest attacks will deprive tens of thousands of life-saving care," the ICRC said.

Both Eastern Ghouta and Idlib are among four so-called de-escalation zones in Syria, which were delineated last year as part of a ceasefire proposal meant to end hostilities between rebel and government forces.