At least 10 people were killed on Wednesday in an airstrike that hit a group of farmers in a vegetable market in Yemen's Hodeida province, medical workers and residents said.
A Saudi-led coalition that intervened in Yemen's war in 2015 has conducted frequent airstrikes targeting the Iran-aligned Houthi group and has often hit civilians, although it denies doing so intentionally.
Medics and residents in Bayt al-Faqih, a town 70 km (40 miles) south of Hodeida city, said nine other people were also wounded in the airstrike.
Houthi media said 19 were killed and 10 were wounded in the same area.
Residents said violent clashes erupted in the southern outskirts of Hodeida, a port city that pro-government forces have been trying to capture from the Houthis since the renewal of an offensive in September.
A spokesman for the Saudi-led coalition, Col. Turki al-Malki, said the alliance is investigating the incident.
"We take this report very seriously and it will be fully investigated, as all reports of this nature are, using an internationally approved, independent process. Whilst this is ongoing, it would be inappropriate to comment further," he said.
The coalition entered Yemen's conflict after the Houthis ousted the internationally recognized government of President Abd-Rabbu Mansour Hadi.
The war has killed more than 10,000 people, displaced more than 2 million and driven the country, already the poorest on the Arabian Peninsula, to the verge of widespread famine.