Aircraft from the Saudi-led coalition battling Shiite rebels in Yemen struck targets in several cities on Sunday, including the capital, security officials said, as fighting raged across the country.

The continued airstrikes and combat between rival factions on the ground underline how a negotiated peace remains elusive in the Arab world's poorest country. They also come despite a Saudi announcement last week saying coalition operations would scale down and shift to focus on diplomacy, humanitarian and counter-terrorism issues.

The Sunday airstrikes began just after midnight, officials said, hitting a military base known to be an arms depot on the outskirts of Sanaa, as well as sites near the presidential palace where weapons were being moved. Fierce street battles in the central city of Taiz killed some 20 civilians and wounded dozens, they added, with mortar rounds fired indiscriminately and landing near a hospital at one point.

In the southern port city of Aden, they said air raids targeted the rebels, known as Houthis, as street fighting between them and forces loyal to embattled President Abed Rabbo Mansour Hadi continued. The officials all spoke on condition of anonymity because they were not authorized to brief journalists.

The Houthis are allied with military units loyal to former President Ali Abdullah Saleh. Although Hadi is Yemen's internationally recognized leader, he was forced to flee the capital and later fled the country as the Houthis advanced toward his stronghold of Aden last month. The Saudi-led coalition began conducting airstrikes against rebel positions on March 26.

Hadi is now in the Saudi capital of Riyadh. The Houthis still control much of the country.

Also Sunday, pro-Saleh forces battled tribesman in the central Marib province, where coalition airstrikes also hit targets. The officials added that the jets also struck pro-rebel sites in Shabwa and Lahj provinces.

The Sunni Arab countries in the coalition and their Western supporters say the Houthis get their arms from Shiite powerhouse Iran, something both Tehran and the rebels deny.

The United Nations said Friday that the war has killed over 550 civilians in the past month, including 115 children.