Five pro-government soldiers were killed and 19 wounded in clashes with jihadists in Yemen's southern city of Taez on Monday after the killing of an aid worker with the International Committee of the Red Cross, medics said.
It was unknown if there were any casualties among the jihadists.
Fighting in the city's Jahmaliah district came after the governor of Taez launched an operation against jihadists he suspected were behind the murder of the ICRC employee over the weekend.
Jahmaliah is controlled by pro-government forces but there is a jihadist presence in the area, a police officer told AFP.
A large portion of Yemen's third city Taez is held by pro-government fighters, but the entrances to the city are controlled by Huthi rebels.
Fierce clashes broke out after the operation was launched on Monday morning, according to the officer, who was unable to provide further details.
On Sunday, Taez governor Amin Ahmad Mahmud, loyal to President Abedrabbo Mansour Hadi, created a special force of police and army units tasked with battling jihadists he believes killed the ICRC employee on Saturday.
The Lebanese aid worker, Hanna Lahoud, was shot in Taez by unidentified assailants.
In March, Yemen entered its fourth year of war between the Iran-backed Huthi rebels and pro-government forces backed by a Saudi-led military coalition.
Nearly 10,000 people have been killed in the conflict, which has triggered what the United Nations has called the world's worst humanitarian crisis.
Sunni jihadists, including from Al-Qaeda and the Islamic State group, have taken advantage of the chaos to expand their influence in parts of Yemen, particularly in the south.