BEIRUT - The Russian-backed Syrian government's air campaign against rebels is widely using cluster munitions, banned by more than 100 countries because of their indiscriminate nature, Human Rights Watch said in a report released on Thursday. The rights group said it had documented 47 cluster munitions attacks, which killed or wounded dozens of civilians in opposition-controlled territory in the last two months. Cluster munitions are containers that explode in the air to distribute smaller bombs over a large area. 'Since Russia and Syria have renewed their joint air operations, we have seen a relentless use of cluster munitions,' said Ole Solvang, HRW's deputy emergencies director. 'The Russian government should immediately ensure that neither its forces nor Syria's use this inherently indiscriminate weapon.'