An air strike by warplanes from a Saudi-led coalition, which said it targeted a bomb-making factory, killed 36 civilians working at a bottling plant in the northern Yemeni province of Hajjah on Sunday, August 30 residents said, according to Reuters.

In another air raid on the capital Sanaa, residents said four civilians were killed when a bomb hit their house near a military base in the south of the city.

The attacks were the latest in an air campaign launched in March by an alliance made up mainly of Gulf Arab states in support of the exiled government in its fight against Houthi forces allied to Iran.

Coalition spokesman Brigadier General Ahmed Asseri denied the strike had hit a civilian target, saying it was a location used by the Houthis to make improvised explosive devices and to train African migrants whom they had forced to take up arms.

He accused the Houthis of using African migrants, stuck in Yemen after arriving by sea before the war in the hope of crossing the Saudi border and finding work in the oil producer, as cannon fodder in dangerous border operations.

Human rights group Amnesty International said in a report this month that the coalition bombing campaign had left a "bloody trail of civilian death" which could amount to war crimes.

Air strikes killed 65 people in the frontline city of Taiz last Friday, most of them civilians, and the bombing of a milk factory in Western Yemen in July killed 65 people including 10 children.

More than 4,300 people have been killed in five months of war in Yemen while disease and suffering in the already impoverished country have spread.

Militias and army units loyal to President Abd-Rabbu Mansour Hadi, currently taking refuge in Saudi Arabia, have made significant advances toward the Houthi-controlled capital in the last two months but the group remains ensconced in Yemen's north and casualties mount in nationwide combat every day.