Human Rights Watch: 'Strong evidence' Syrian army again used chemical weapons last month

A leading human rights group says it has "strong evidence" that Syria's army used chemical weapons on rebel-held areas last month.

Human Rights Watch said on Tuesday that forces loyal to President Bashar Assad likely used chlorine gas on three towns in northern Syria in mid-April.

The New-York based group says chlorine canisters appear to have been embedded into crude explosive-laden barrels, which military helicopters dropped at the time on rebel-held areas.

HRW says that's according to interviews with witnesses, video footage and photographs.

The claim adds to growing concerns that Syria's government is still using chemical weapons, months after a chemical attack killed hundreds of civilians last August.

In late April, the U.N.'s chemical watchdog said it will investigate the chlorine claims.