A group monitoring the Syrian civil war has claimed that Government forces have carried out a poisonous gas attack that has killed six people in the northwest of the country.

The Syrian Observatory for Human Rights says the six dead included a man, his wife and their three children. It says the gas was dispersed by barrel bombs and was likely chlorine.

Medics posted videos of children suffering from what they say was gas-induced suffocation.

The Syrian government has previously denied accusations that it has used chemical weapons in the four-year-old war.

The report has not been independenty verified.