SANAA: Warplanes from a Saudi-led coalition kept up their airstrikes targeting the positions of Yemen's Shiite rebels and their allies around the capital, Sanaa, hours ahead of a humanitarian cease-fire set to begin Tuesday evening.

The strikes stopped shortly before the newly appointed U.N. envoy to Yemen, Ismail Ould Cheikh Ahmed of Mauritania, flew into Sanaa on his official first visit to the country. He told reporters he planned to meet with various parties, including the rebels known as Houthis, and ensure that the cease-fire holds.

According to security officials, airstrikes overnight, at dawn and during the morning hours targeted weapons depots and other military facilities north and south of Sanaa, a sprawling city of some 4 million people. The military air base that is part of the capital's international airport was also targeted.

In all, Sanaa endured a total of 10 strikes from dawn until about noon Tuesday, the officials said, speaking on condition of anonymity because they were not authorized to talk to the media.

The cease-fire, scheduled to begin at 11 p.m., is meant to help ease the suffering of civilians in Yemen, the Arab world's poorest country.

The conflict has killed over 1,400 people - many of them civilians - since March 19, according to the U.N., and the country of some 25 million has endured shortages of food, water, medicine and electricity as a result of a Saudi-led naval, air and land blockade.

Tuesday's airstrikes came one day after the coalition pounded a mountainside on the northeastern edge of Sanaa, hitting arms and ammunition depots. The bombardment shook the entire city, collapsing some homes and shattering windows. They also caused shells to explode from the arms depots, and the munitions hit residential areas and started fires.

The health Ministry said Tuesday that preliminary figures show that Monday's airstrikes in Sanaa killed 10 and wounded 162, mostly civilians.

The officials said the strikes were among the strongest in Sanaa since the air campaign began March 26 against the Houthi rebels and their allies in the army and security forces loyal to former President Ali Abdullah Saleh.

Saudi Arabia and its coalition of Sunni Arab countries began the airstrikes to break the advance of the Houthis and Saleh's forces, who overran Sanaa and much of northern Yemen late last year and have been on the offensive in the south. The Saudis and their allies are seeking the restoration of President Abed Rabbou Mansour Hadi, who fled the country in March in the face of the Houthi advance.

Also Tuesday, Human Rights Watch said the Houthis have intensified the recruitment, training, and deployment of children in the conflict in violation of international law. Since the rebels seized Sanaa in September, it said, the Houthis have increasingly used children as scouts, guards, runners, and fighters, with some children being wounded or killed.

"The Houthis and other armed groups using child soldiers in Yemen should immediately stop recruiting children, including 'volunteers,' and release all children in their ranks," it said.

The security officials said Monday the Houthis were recruiting boys as young as 15 in Sanaa to fight in Saada, the rebel stronghold north of the capital, against Sunni tribesmen trying to enter the province that sits along the border with Saudi Arabia.

Islamic militant websites, meanwhile, said Tuesday that four leading members of Yemen's Al-Qaeda branch were killed the previous day in a suspected U.S. drone strike in a southern port city.

The four died in Mukalla on the Arabian Sea, where rockets believed to have been fired by U.S. drones hit Al-Qaeda militants based in the city's presidential residence, according to security officials.

The militant Aamaq outlet, affiliated with the more extreme Islamic State group, said the four included Maamoun Hatem, reportedly an ISIS sympathizer. The three other militants were identified as Abu Anwar al-Kutheiri, Mohammed Saleh al-Ghorabi and Mabkhout Waqash al-Sayeri.

The compound in Mukalla was recently captured by al-Qaida's branch in Yemen, viewed by Washington as the terror group's most dangerous affiliate.