Medics in Yemen say at least 41 civilians have been killed and 75 others wounded in an air strike by Saudi-led coalition warplanes in the north of the country.

Key points: Air strike hits outdoor market in Mustaba district killing several children

Air strike hits outdoor market in Mustaba district killing several children Strikes are aimed at Houthi rebels, seeking to overthrow the Yemen government

Strikes are aimed at Houthi rebels, seeking to overthrow the Yemen government More than 6,000 people killed since air raids began in March 2015

Witnesses said at least two missiles hit a busy market in the northwest province of Hajjah.

Video footage purportedly of the aftermath of the airstrike showed what appeared to be the bodies of several children.

The director of the Hajjah health department, Ayman Mathkour, said three of Tuesday's air raids hit an outdoor market in the Mustaba district.

He said relatives gathered the bodies and took the wounded to Abs and Mustaba hospitals.

An official at a hospital run by Doctors Without Borders (MSF) said the facility had received the bodies of 41 people killed in the raids, along with 35 people who were wounded.

It was not immediately clear why the coalition targeted the market in Mustaba and there was no word yet from the Arab alliance led by Yemen's neighbour Saudi Arabia on the raids.

Saudi Arabia, the United Arab Emirates and a coalition of other Sunni Arab countries has been conducting airstrikes in Yemen since last March, to stop opposition Houthi forces from seizing the whole country.

Coalition strikes killing thousands of civilians: UN

The United Nations says over 6,000 people; half of them civilians have been killed since the air campaign began.

In January, a UN panel found the strikes had targeted civilians and recommended an investigation into possible war crimes.

Rights groups have repeatedly urged the coalition to avoid causing civilian casualties.

Last month, Human Rights Watch accused the coalition of using US-supplied cluster bombs.

The coalition said an independent inquiry would examine charges of possible abuses against civilians in the conflict.

A panel of UN experts says the coalition has carried out 119 sorties that violated humanitarian law, and called for an international probe.

In February, a coalition air strike on a market northeast of rebel-held capital Sanaa killed at least 30 rebels and civilians, according to witnesses.

It targeted three rebel vehicles as they entered the market.

Last week, the coalition launched air strikes against jihadists in Aden, for the first time since it started its campaigns last year against the rebels.

The World Health Organisation says more than 6,200 people have been killed in the conflict since March 2015 and the United Nations has warned of a "human catastrophe unfolding in Yemen".