The Syrian government has used internationally banned cluster munitions in attacks on a besieged rebel-held suburb of Damascus, committing war crimes on "an epic scale", Amnesty International has said.
Eastern Ghouta, a rebel-held suburb north-east of the Syrian capital, has been under a tightening siege since 2013 and is already facing a humanitarian crisis, including the highest recorded malnutrition rate since the conflict began in 2011.
Some 400,000 civilians, half of them children, are believed to be trapped there.
Based on interviews with activists in Eastern Ghouta and verification of open source videos and photographs, Amnesty said at least 10 civilians were killed in November because of the government's use of the banned Soviet-made cluster munitions.
The indiscriminate weapons, banned in more than 100 countries, gravely endanger civilians because of their indiscriminate nature, Amnesty said.
"The Syrian government has shown callous disregard to the lives of the hundreds of thousands of people living in Eastern Ghouta," said Philip Luther, Amnesty International's research and advocacy director for the Middle East and North Africa.
"But this recent escalation in attacks - clearly targeting civilians and civilian infrastructure using internationally banned cluster munitions - is horrific."
Amnesty said the cluster munitions first appeared in Syria after Russia began strikes against anti-government groups in September 2015.
Witnesses interviewed by Amnesty said they saw cluster munitions projectiles - small bombs strapped to parachutes - used in densely populated market and residential areas.
The United Nations has said it is concerned about the ongoing violence in Eastern Ghouta.
The Britain-based Syrian Observatory for Human Rights, which tracks the civil war, has recorded that at least 150 civilians, including 35 children, have been killed in the suburb since November 14, when a renewed round of intense fighting began.
Russia informed the UN on Tuesday that the Syrian government had agreed to a 48-hour truce in the area at the start of a new round of UN-sponsored talks in Geneva.
Diplomats are hoping that the parties to the Syrian conflict may be ready to make some forward progress in talks, which formally got under way with the arrival of the government delegation in Switzerland on Wednesday.
There is little optimism, however, that the current round - the eighth so far - would achieve any significant breakthroughs.
On Thursday, the Syrian government and opposition delegations in Geneva met separately with the UN envoy, Staffan de Mistura.