Human Rights Watch says it has evidence that Syrian regime forces have carried out hundreds of indiscriminate attacks over the past year with air-delivered munitions, including improvised weapons such as barrel bombs.
The US-based group says the attacks have had a devastating impact on civilians, killing or injuring thousands of people.
Barrel bombs are crudely made containers filled with nails, metal shrapnel and explosive which are dropped from helicopters.
Regime forces have repeatedly been accused on using these munitions during the war despite a UN resolution last year banning their indiscriminate use in populated areas.
"For a year, the Security Council has done nothing to stop Bashar al-Assad's murderous air bombing campaign on opposition-held areas, which has terrorized, killed, and displaced civilians," said Nadim Houry, deputy Middle East and North Africa director at Human Rights Watch.
People inspect a site hit by a barrel bomb, dropped by forces loyal to Syria's President Bashar al-Assad, in the al-Myassar neighborhood of Aleppo, February 7, 2015.