More than a dozen civilians were killed in the first half of April in Yemen’s southeastern Ma’rib Governorate, the UN said on Tuesday.  

“As hostilities continue, civilian lives continue to be at risk, with the Civilian Impact Monitoring Project reporting at least 14 civilian casualties in the first half of April,” the UN Office for the Coordination of Humanitarian Affairs said in a statement.

Intensified clashes continue across frontline areas in Ma’rib, with hostilities particularly rife in the Sirwah district located in the west of Ma’rib, it said.

Rising tension caused a large migration wave within the governorate since the escalation began in early February, it added.

In recent weeks, Houthi rebels have stepped up attacks to take control of oil-rich Marib province, one of the most important strongholds of the legitimate government and home to the headquarters of the Yemeni Defense Ministry.

The Yemeni army launched a large-scale operation on Feb. 13 against the rebels on various fronts in Marib.

Yemen has been ravaged by violence and instability since 2014, when Houthi rebels captured much of the country, including Sana’a.

The crisis escalated in 2015 when the Saudi-led coalition launched a devastating air campaign aimed at rolling back Houthi territorial gains.

It has since caused one of the world’s worst man-made humanitarian crises, with 80% of the population, in need of assistance and protection.