Saudi-led coalition air strikes Monday on a hospital in a rebel-held town in northern Yemen killed at least six people and wounded 20 others, a rebel health official said.

Ayman Mazkour, who heads the health sector in Hajja province, warned however that the toll could rise.

"Medical teams have not yet been able to enter the hospital," he said in a statement carried by the rebel sabanews.net website, adding that coalition warplanes were still flying over the area.