SANAA/ADEN, Yemen: Arab-led coalition airstrikes have killed 28 Houthi rebels around Yemen’s west coast, medics and security sources close to the insurgents said Friday, as government forces reported deadly clashes in the south. The security sources said airstrikes Thursday and Friday hit five towns controlled by the Houthis around 70 kilometers south of Red Sea port city of Hudaida. Medical sources said 28 Houthis were killed and 17 wounded in the attacks.

Houthi rebels stepped up fighting with forces loyal to the internationally recognized government of President Abed Rabbou Mansour Hadi along Hudaida and southern Yemen.

Foreign humanitarian workers with the United Nations and other international organizations have left Hudaida because of intensified fighting there, Yemeni officials said Friday, leaving local employees to carry out the humanitarian work.

In their push toward Hudaida, Hadi’s forces have made military advances over the past week, capturing several rebel-held areas, including the coastal district of Al-Khoukha, about 135 kilometer from the port city.

The Houthis, however, claimed their forces were able to regain control of some areas captured by Hadi, allegedly killing more than 120 of their enemies over the past three days.

Tribal officials Friday said Hadi’s forces seized several rebel-held areas in the southern province of Shabwa, including the district of Bayhan which has been under Houthi control since 2015. Bahyan’s was captured during clashes that left 14 rebels and nine pro-government troops dead, the officer said.

Bayhan is crucial in Yemen’s war because of its location on a major road linking Shabwa province with Houthi-held Maarib province to the north. The army’s advance means that the Houthis have been expelled from Shabwa, sources said.

In the southwestern province of Taiz, suspected Arab-led coalition airstrikes killed at least eight civilians and wounded 15 others, officials also said.

Fighting has escalated between the rebels and Hadi’s forces after the killing of Yemen’s ex-president, Ali Abdullah Saleh, earlier this month at the hands of his onetime allies, the Houthis.

Separately, France reacted cautiously Friday to U.S. evidence that allegedly proved Iran supplied weapons to the Houthis, saying it was still studying information at its disposal and the U.N. had yet to draw any conclusions.

The United States Thursday presented for the first time military pieces of what it said were Iranian weapons supplied to the rebels, describing it as conclusive evidence that Tehran was violating U.N. resolutions.

When asked whether Paris believed that the evidence provided by the U.S. was irrefutable, foreign ministry deputy spokesman Alexandre Giorgini declined to respond directly.

“The United Nations secretariat has not, at this stage, drawn any conclusions. France continues to examine the information at its disposal,” he said.