Yemeni girls play with a vehicle damaged by Saudi-led coalition airstrikes in Sanaa, Yemen, on May 18. Saudi-led airstrikes targeting Yemen's Shiite rebels resumed early Monday in the southern port city of Aden after a five-day truce expired. (Hani Mohammed/AP)

Warplanes from a Saudi-led coalition struck targets in Yemen on Monday and ground clashes resumed, bringing a sharp end to a five-day cease-fire in the conflict and raising fears that a humanitarian disaster would deepen.

More than 1,600 people have been killed in the war between the Houthi rebels and supporters of the country’s ousted president, who are backed by the military alliance led by Saudi Arabia. The five-day “pause” was intended to allow aid to reach Yemenis suffering from dangerous shortages of medicine, fuel and food. But many Yemenis complained Monday that supplies had not reached their areas.

“Now we are at the edge of a big catastrophe” in the humanitarian situation, said Cédric Schweizer, who headed the International Committee of the Red Cross delegation in Yemen until last week.

The temporary cease-fire was “a good first step, but it will not solve the humanitarian crisis,” Schweizer said in an interview with Washington Post reporters in Washington.

“All hospitals are lacking basic medicines now,” he added. Yemenis are running out of money to buy ever-more-expensive food, he said.

An armed Houthi militiaman stands in front of graffiti on a wall commemorating the victims of an airstrike in Sanaa on May 18 by the Saudi-led coalition. Airstrikes aimed at the Houthi rebel group targeted the key southern Yemeni city of Aden and areas in the north. (Yahya Arhab/EPA)

U.N. and U.S. officials had hoped the cease-fire would be extended. But on Monday, airstrikes hit several locations in the southern city of Aden, as well as in the Houthi-dominated province of Saada near the Saudi border, local media reported. Houthis and their opponents clashed in the southwestern city of Taiz and other areas.

Saudi Arabia launched the airstrikes in March in a bid to push Houthi fighters, who are Shiite, from territory that they seized in recent months. Saudi officials have said they want to restore to power Yemeni President Abed Rabbo Mansour Hadi, who has fled the country. They have accused Iran of backing the Houthi militias.

Local media reported multiple raids Monday on the airport in Aden, which would jeopardize plans to bring in aid on humanitarian flights to the city.

The Saudi-led coalition has imposed an air, land and sea blockade on Yemen, according to aid groups. International aid agencies scrambled to move assistance into Yemen during the temporary truce, which took hold May 12.

“Everything you can imagine is needed: drinking water, shelter, food, medicine,” said ­Mohammed Abu Asaker, a communications officer with the U.N. refugee agency who is based in the United Arab Emirates. “The situation there is extremely dire.”

Purnima Kashyap, the World Food Program’s Yemen country director, said the agency’s first goal was to get fuel to trucks to transport aid to the agency’s warehouses, which are scattered across the country and are to be hubs of further distribution.

In Sanaa, Yemen’s capital, a small amount of gasoline became available, but residents had to wait in long lines for it.

Ridwan Mohammed, a 40-year-old employee of a pharmaceutical company, said he had waited in a gas line for two days.

“Now that the cease-fire is over, I feel more tense,” he said. “I am worried that an airstrike could happen at any time.And I am out here waiting.”

Cunningham reported from Cairo. Heba Habib in Cairo contributed to this report.

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