Insurgent groups in Syria have carried out scores of indiscriminate attacks that have killed and maimed civilians in violation of the laws of war, a Human Rights Watch report said on Monday.

The report said armed groups could not point to abuses by government forces and allied militias to justify their own violence, which it said had often targeted areas with a high concentration of religious minorities.

"We've seen a race to the bottom in Syria, with rebel groups mimicking the ruthlessness of government forces with devastating consequences for civilians," said Nadim Houry, HRW's deputy Middle East director.