The Saudi-led coalition's air strikes against Yemen's Shiite rebels and their allies have killed 29 people, including civilians, in the capital Sanaa, according to officials.

The air strikes hit an apartment building in the centre of the capital, a Unesco world heritage site, killing a family of nine, said the security and medical officials, who remain neutral in the conflict that has divided the country's security forces.

One more civilian was killed and the search for more that may be buried under rubble is ongoing.

The rebels known as Houthis lost 19 fighters in the overnight attack.

Yemen is torn by ferocious fighting between the Houthis and their allies against the internationally recognised government's forces backed by the Saudi-led coalition.