U.N. Cease-Fire Fails to Take Hold in Yemen

AL MUKALLA, Yemen — A cease-fire brokered by the United Nations that was intended to allow the delivery of relief supplies failed to take hold in Yemen on Saturday, as a military coalition led by Saudi Arabia carried out airstrikes, and fighting continued between the Houthis rebels and rival militias in several cities.

The “pause” in the fighting had been scheduled to begin before midnight on Friday and was to last for a week. United Nations officials said that both Yemen’s Saudi-backed government in exile and the Houthis, who control large parts of Yemen, had agreed to the truce.

But Saudi Arabia, which launched a military offensive in March to defeat the Houthis said Saturday that it had received no request from the Yemeni government, which is based in Riyadh, the Saudi capital, to comply with a humanitarian truce.

A Saudi military spokesman, Brig. Gen. Ahmed al-Assiri, accused the Houthis of not accepting the truce publicly while their fighters continued to advance in several cities. “Who will be on the ground to observe the Houthis?” he said in an interview, adding that the “minimum requirements” had not been met for a successful pause in the fighting.

General Assiri’s comments underscored the difficulties diplomats have faced negotiating even the briefest halt to hostilities in Yemen’s complex and multisided war. And they were a public blow to efforts by United Nations officials, who had suggested that the most intractable disagreements between the combatants could be settled at some later date.

Relief officials have said that millions of Yemenis are facing famine as a result of the fighting, which has blocked virtually all shipments of food into the country. Hospitals have run out of medicine, as well as fuel to run generators. In areas of the country worst affected by the combat, drinking water is scarce, and health officials have reported outbreaks of dengue fever.

Airstrikes by the Saudi-led coalition continued for hours after midnight on Saturday, according to residents in Sana, the Yemeni capital. In Taiz, in central Yemen, the coalition conducted at least a dozen strikes in the city between midnight and 11 a.m., according to Ali al-Sarari, a local human rights activist.

The city’s rival militias had also failed to heed the call for a cease-fire, he said. The Houthis, who are allied with security units loyal to a former Yemeni president, shelled several areas on Saturday that are under the control of local militias who oppose the Houthis.

In Aden, a southern port city that has been devastated by months of war in Yemen, residents described fierce clashes between the Houthis and their local opponents.

“There is no humanitarian truce here,” said Abdul Nasser al-Wali, who runs a local association for volunteer doctors. Health workers had been trying for months to evacuate hundreds of wounded people from the city, Mr. Wali said.

“No aid ships arrived today,” he said.