The Syrian regime is expanding its use of widely banned cluster bombs, an international human rights group said in a report today as the deadlocked conflict entered its third year.

In the past six months, Syrian forces have dropped at least 156 cluster bombs in 119 locations across the country, causing mounting civilian casualties, the New York-based group Human Rights Watch said.

Two strikes in the past two weeks killed 11 civilians, including two women and five children, the report said. The group said it based its findings on field investigations and analysis of more than 450 amateur videos.

Cluster bombs open in flight, scattering smaller bomblets. They pose a threat to civilians long afterwards since many don’t explode immediately. Most countries have banned their use.

The report came a day after Syrians marked the second anniversary of their uprising against President Bashar Assad. The rebellion began with largely peaceful protests but in response to a harsh regime crackdown turned into an insurgency and, by last summer, into a full-scale civil war.

The fighting has killed some 70,000 people and displaced four million of Syria’s 22 million people, according to UN estimates.

The conflict remains deadlocked, despite some recent military gains by the rebels who control large stretches of northern and eastern Syria.

The regime routinely pounds rebel strongholds with artillery and drops bombs from the air, sending civilians fleeing.

Assad has been digging in, particularly in the densely populated western part of the country. He has armed and mobilised loyalists, and repelled rebel attacks on his seat of power, the capital Damascus.

The rebels have appealed to the West for military aid, including anti-aircraft weapons, to help them break the stalemate.