A health official in Hajja said the casualties were civilians and included children, adding that "the toll could rise".
Local officials and tribal sources told AFP that coalition warplanes carried out several raids on the market in the town of Mustabaa.
The rebel-run sabanews.net website said that the coalition carried out two raids targeting the market and a restaurant in the area and gave a toll of 65 civilians dead and 55 wounded.
It quoted an unnamed source as saying that health facilities in Mustabaa and the neighbouring town of Abs were receiving the casualties but were short on medical supplies.
The coalition launched its campaign against Iran-backed rebels in support of the Yemen's internationally-recognised government on March 26 last year.
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 has said that 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.
But it was not immediately clear why the coalition targeted the market in Mustabaa and there was no word yet from the Arab alliance led by Yemen's neighbour Saudi Arabia on the raids.
The Shiite Huthi rebels advanced from their northern strongholds seizing Sanaa in September 2014 before expanding further towards the south.
They forced President Abedrabbo Mansour Hadi to flee with members of his government to Saudi Arabia before later declaring main southern city Aden as the temporary capital.
But Al-Qaeda and the Islamic State group are becoming increasingly active in Aden, where they have carried out deadly attacks.
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".
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