The latest deaths come ahead of UN-brokered peace talks set to take place between the warring parties in Switzerland on Tuesday.
A government-proposed seven-day ceasefire is expected to coincide with the negotiations.
Air strikes by the Arab coalition on the Haradh area of the northern province of Hajja hit six homes, witnesses said.
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"We received the bodies of 12 civilians and more than 20 others were wounded," an official at a field hospital in Haradh said.
Haradh, on the border with Saudi Arabia, is among the northern strongholds of the Shia Huthi rebels who control Yemen's capital.
Along with their allies, the Iran-backed Huthis have been targeted by the coalition since March.
In the south, 12 rebels were killed when loyalist artillery hit two rebel vehicles near the city of Damt, which the Huthis and their allies captured in November, military sources said.
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In the same area, nine rebels and four pro-government fighters were killed in clashes late Saturday, the sources said.
Further west, coalition warplanes early on Sunday struck a rebel military convoy between the strategic Taez province and Lahj in the south, killing seven people, tribal sources said.
The Huthis, allied with renegade troops loyal to former president Ali Abdullah Saleh, claimed on their sabanews.net website to have fired a missile at the Saudi Khaled bin Abdulaziz base in the kingdom's south, causing damage.
The rebels frequently make such claims, and Saudi authorities did not confirm the incident.
A truce is much needed in the Arabian Peninsula's poorest nation where an estimated 80 percent of the population of 26 million needs aid.
The United Nations says more than 5,800 people have been killed in Yemen, about half of them civilians, and more than 27,000 wounded since March.
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