At least 21 civilians were killed in two separate air strikes by the Saudi-led coalition in northern Yemen on Saturday, residents said on Sunday, as fighting intensified in the country before the Muslim Eid al-Adha feast.

They said at least 15 civilians were killed when war planes targeted workers drilling for water in the Beit Saadan area of the Arhab district north of Sanaa, and that 20 other people were wounded.

Residents said Saudi-led coalition warplanes, apparently mistaking the drilling machine for a rocket launcher, bombed the site and killed four workers. The planes conducted a second raid when residents of the village rushed to the scene, killing at least 11 more and wounding 20.

A spokesman for the Saudi-led coalition could not immediately be reached for a comment. The coalition, which has been fighting to roll back gains made by the Iran-allied Houthi group since 2014 and restore ousted President Abd-Rabbu Mansour Hadi to power, says it does not target civilians.

UN-sponsored talks to try to end the fighting collapsed in failure last month and the Houthi movement and allied forces loyal to former president Ali Abdullah Saleh resumed shelling into neighbouring Saudi Arabia.

Saturday's attacks were the latest in a series of strikes that have hit schools, hospitals, markets and private homes.

Local media put the number of dead and wounded at the water-drilling site at around 100 and published pictures of burned bodies and mangled equipment, and videos showed workers collecting mutilated bodies and carrying them away in blankets.

In the second attack on Saturday, residents reported an air strike hit the home of Sheikh Maqbool al-Harmali, a local tribal chief in Hairan district of Hajjah province, killing six civilians.

The UN says more than 10,000 people have been killed in the fighting, many of them civilians.