Three Yemeni soldiers were killed Saturday when a mine they had "dismantled" and taken away in their vehicle blew up as they stopped in a marketplace, a security official said.

Seven other people including three civilians were wounded in the blast in Huta, capital of the southern province of Lahj, a bastion of Al-Qaeda extremists, according to the official.

The soldiers had "dismantled" the mine planted by suspected jihadists on a road on the edge of Huta and placed it in the back of their vehicle, he said, declining to be named.

The device exploded when they stopped at a market in the city, he added.

Forces loyal to President Abedrabbo Mansour Hadi, backed by a Saudi-led Arab coalition, are at war on two fronts, against both militants and Shiite Huthi rebels who control swathes of northern and central Yemen.

On Friday, the Huthis announced on their sabanews.net website that they had fired a modified Scud missile with an extended range of 800km (500 miles) at Saudi territory.

The conflict in Yemen has cost more than 6,600 lives and displaced at least three million residents of the impoverished country since the coalition's intervention in March 2015, according to UN figures.