NEW YORK (Thomson Reuters Foundation) - An ambulance driver working with Doctors Without Borders has been killed in an air strike in Yemen, the medical charity said on Friday (Jan 22), the latest attack on the group's workers and facilities.

The ambulance was hit by an air strike on Thursday in Dhayan, in Saada province in north Yemen, the group said.

The driver was described as a Yemeni Ministry of Health employee, it said.

The attack was the fourth to hit the group's medical operations in the war-torn Arabian Peninsula country, a spokesman told the Thomson Reuters Foundation.

"This latest loss of a colleague is devastating, and it demonstrates the ruthlessness with which healthcare is coming under attack in Yemen," Ms Teresa Sancristoval, emergency coordinator, said in a statement.

Earlier this month, a blast at a clinic near the city of Saada killed six people, the group said.

Other attacks occurred in October and December, when air strikes damaged medical facilities near Taiz city and in Saada province's Haydan district, it said.

A military coalition led by Saudi Arabia has been fighting the Iran-allied Houthi group in Yemen, and nearly 6,000 people have been killed since the conflict began in March.