Seven people, including four children, were killed in an air raid near a hospital in a rural area of northwest Yemen, aid group Save the Children said.
The organisation, which supports the hospital, said in a statement sent to the Associated Press news agency that two adults were also unaccounted for after the attack on Tuesday.
Save The Children said a missile struck a petrol station near the entrance to Kitaf rural hospital, about 100km from the city of Saada, at 9:30am local time.
“The missile was said to have landed within 50 metres of the facility’s main building,” it said.
The organisation said the hospital had been open for half an hour and many patients and staff were arriving on a busy morning.
Among the dead were a health worker and the worker’s two children and a security guard, it said.
Save the Children, which reported earlier this week that on average 37 Yemeni children a month had been killed or injured by foreign bombs in the last year, demanded an urgent investigation into the attack.
Helle Thorning-Schmidt, the organisation’s chief executive, said: “We are shocked and appalled by this outrageous attack.
“Innocent children and health workers have lost their lives in what appears to been an indiscriminate attack on a hospital in a densely populated civilian area,” she said. “Attacks like these are a breach of international law.”
Thorning-Schmidt said the hospital is one of many Save the Children supports in Yemen, “but time after time, we see a complete disregard by all warring parties in Yemen for the basic rules of war.”
A Saudi-led coalition allied with the internationally recognised government of President Hadi has been fighting the Houthis since 2015.
Air raids by a coalition led by Saudi Arabia and the United Arab Emirates have hit schools, hospitals and wedding parties, killing thousands of Yemeni civilians. The Houthis have fired long-range missiles into Saudi Arabia and targeted vessels in the Red Sea.
The fighting in the Arab world’s poorest country has killed thousands of civilians, left millions suffering from food and medical shortages, and pushed the country to the brink of famine.
UN humanitarian chief Mark Lowcock has said about 80 percent of Yemen’s population – 24 million people – need humanitarian assistance, including nearly 10 million “just a step away from famine” and nearly 240,000 “facing catastrophic levels of hunger”.
Thorning-Schmidt called for an immediate suspension of arms sales to the warring parties and diplomatic pressure to end the conflict.
“We must stop this war on children,” she said.