The air strike targeted three rebel vehicles as they entered a market in the town of Naqil bin Ghaylan, killing at least 30 Houthi insurgents and civilians, one tribal source in the area said.
The rebel-controlled Saba news agency gave a higher death toll, saying that 60 civilians were killed and wounded in the attack but it did not mention any casualties among fighters.
The attack hit Khulaqa market, which is known for selling qat, a mild narcotic that is chewed throughout Yemen, witnesses said.
The area is part of the Nehm region, where coalition-backed loyalists have been advancing against the rebels as they try to close in on Sanaa.
Rights groups have repeatedly urged the coalition to avoid causing civilian casualties.
Earlier this month, Human Rights Watch accused the coalition of using US-supplied cluster bombs.
The coalition last month announced 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.
The coalition launched late March 2015 an air campaign against Iran-backed rebels in support of the UN-recognised President Abedrabbo Mansour Hadi.
The Iran-backed Shiite rebels have controlled Sanaa since September 2014 and had placed Hadi under house arrest.
But he escaped, initially seeking refuge in second city Aden last year before fleeing to the Saudi capital, Riyadh, as the rebels advanced on the southern port.
Hadi returned to Aden after loyalists backed by the coalition drove the rebels out of there and four other southern provinces in the summer.
But Hadi and senior officials continue to spend most of their time in Riyadh against a backdrop of worsening security in Aden, the temporary base of the government.
The United Nations warned this month of a "human catastrophe unfolding in Yemen", where it says more than 6,100 people had been killed in the fighting since last March.
The UN said another 3,000 people had been wounded and 2.5 million people forced to flee their homes.
Donors at a conference in Qatar pledged Wednesday $220 million of aid to Yemen.
Hadi's government accused this week Lebanon's Hezbollah of sending fighters to support the Houthis, saying it had evidence of the Shiite militia's involvement.
Also on Saturday, the United Arab Emirates, a key member of the Saudi-led coalition, said that one of its soldiers has died in Yemen when his military vehicle overturned.
The UAE has lost more than 70 soldiers in Yemen since the launch of the campaign.
