At least 15 Houthi rebels were killed Monday in Yemen amid clashes with army troops and Saudi-led coalition forces, the Houthi-run Saba news agency said.

The report did not include details on the clashes.

Yemen has been beset by violence and chaos since 2014, when Houthi rebels overran much of the country, including the capital Sanaa.

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

More than 100,000 Yemenis, including civilians, are believed to have been killed in the conflict, which has led to the world’s worst humanitarian crisis, with millions at risk of starvation.