Renewed Syrian army bombardment of rebel-held Eastern Ghouta outside Damascus on Monday killed 14 people, despite a ceasefire deal for the region, a monitor said.

Eastern Ghouta, one of the last remaining opposition strongholds in Syria, is among four so-called "de-escalation zones" set up earlier this year under a deal agreed by regime allies Russia and Iran, and rebel supporter Turkey.

But despite the deal, violence has spiralled in the area in recent days.

On Monday, air strikes and artillery fire on several parts of Eastern Ghouta killed at least 14 civilians, the Britain-based monitor Syrian Observatory for Human Rights said.

The deaths come a day after at least 23 civilians were killed in the region in regime air strikes and artillery fire, among them four children.

The Observatory says regime bombardment of Eastern Ghouta has killed more than 100 people in the past two weeks.

Rebels have also fired from the area into Damascus in deadly attacks of a kind rarely seen in the capital.

Eastern Ghouta is already in the grip of a humanitarian crisis caused by a crushing regime siege of the area since 2013 that has caused severe food and medical shortages.

Humanitarian access to Eastern Ghouta has remained limited despite the implementation of the ceasefire zone, and a United Nations official has named the region as the "epicentre of suffering" in Syria.

More than 340,000 people have been killed in Syria since its conflict began in March 2011 with anti-government protests.