MARIB: At least 14 pro-government troops were killed when a Saudi-led coalition air raid targeted their position "by mistake", tribal and military sources said Friday.

"The air force bombed a gathering of fighters in the region of Harib believing them to be Houthi rebels," a military source said.

A tribal chief confirmed the overnight strike, saying that those killed appeared to be local tribesmen fighting on the side of the forces loyal to exiled President Abedrabbo Mansour Hadi.

Harib is around 80 kilometres south of Marib, the capital of the central province.

Loyalist forces, backed by the Saudi-led coalition, say they are advancing on the ground in Marib as part of a major counter offensive against Shia Houthi rebels, who last year stormed Yemen's capital and seized large parts of the country.

Coalition aircraft launched a series of raids Friday morning on rebel positions in the south of the province, military sources said.

The United Nations (UN) says nearly 4,900 people have been killed and around 25,000 wounded since late March, while 21 million out of Yemen's population of 25 million have been affected by the conflict.

Read: 31 killed as intense Saudi-led coalition raids pound Yemen rebels