The fighting has been taking place in Marib and Shabwa provinces, the officials said, adding that in Shabwa's region of Bihan, along with the 85 killed, about 100 fighters have been wounded on both sides.

Security officials loyal to President Abed Rabbo Mansour Hadi said pro-government forces retreated due to lack of air support from the Saudi-led coalition. All officials spoke on condition of anonymity because they were not authorized to talk to reporters.

Yemen's war pits rebels known as Houthis and their allies against Hadi's forces, backed by the Saudi-led coalition.

Also Thursday, airstrikes by the Saudi-led coalition hit a gathering of the Houthis in the capital, Sanaa, killing five, security officials said.

Meanwhile, a fuel ship sent by the United Arab Emirates arrived Thursday in Yemen's southern port city of Aden, local officials said, where residents have been protesting power shortages. Government forces and allied militiamen retook the city from the Houthis several months ago.

Since Yemen's civil war started, more than 8,100 people have been killed. The United Nations says more than 80 percent of Yemenis are in dire need of food, water and other aid as a result of the conflict in the Arab world's poorest country.