The Shiite Huthi rebels, who have overrun large parts of the country and forced President Abedrabbo Mansour Hadi to flee abroad, have demanded an end to the air war as a condition for UN-sponsored talks.
But the raids continued on Sunday, hitting the rebel-held presidential palace in Sanaa and anti-government positions in the main southern city of Aden, military sources and witnesses said.
Fighting also intensified in Marib province, east of the capital, where Sunni tribes and pro-Hadi fighters clashed with Huthis and allied forces.
A military official said the presidential complex in Sanaa was targeted as reinforcements were being prepared to send to oil-rich Marib.
Aden residents said air raids also targeted rebel positions there, and a medical source said three pro-Hadi fighters and two civilians were killed in clashes with the Huthis.
The rebels lost three men, a pro-Hadi source said.
The United Nations on Saturday confirmed Mauritanian diplomat Ismail Ould Cheikh Ahmed as the new special envoy to Yemen, replacing Moroccan Jamal Benomar who resigned last week following what diplomats described as sharp criticism of his performance by Gulf states.
Ould Cheikh Ahmed "will work closely with the members of the United Nations Security Council, the Gulf Cooperation Council, governments in the region and other partners," a UN statement said.
- 'End external aggression' -
Former strongman Ali Abdullah Saleh, who still holds sway over army units allied with the Shiite rebels, late Friday urged the Huthis to heed UN demands to withdraw from territory they have seized.
US Secretary of State John Kerry also urged anti-government forces to enter into political dialogue to end a conflict the United Nations says has killed more than 1,000 people since late March.
But Mohammed al-Bukhaiti, a member of the Huthis' political bureau, told AFP on Sunday that "dialogue cannot resume before the end of external aggression".
The fighting has raised fears Yemen could become a front in a proxy war between Sunni-ruled Gulf monarchies and Shiite Iran.
Tehran rejects accusations it armed the rebels and has presented a peace plan to the UN calling for a ceasefire and the formation of a unity government.
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A US aircraft carrier headed to Yemeni waters last week to monitor an Iranian convoy that had raised suspicions. It redeployed on Friday after the convoy turned back, Pentagon officials said.
The coalition has kept up air strikes days after announcing its campaign was entering a new phase aimed at resuming the political process, delivering aid and fighting "terrorism".
Marib has been the scene of days of deadly clashes between rebels and fighters loyal to Hadi.
Sunni tribes and pro-Hadi troops battled the rebels and their allies in Marib's Sarwah district, through which Yemen's main oil export pipeline passes, tribal sources said.
- Taez hospital hit -
The 435-kilometre (270-mile) pipeline links Marib's Safir oilfields with the Ras Isa terminal on the Red Sea coast, and control of it has been a key goal for the rebels and their allies.
Tribal sources said 90 rebels were killed in clashes and air strikes in Marib. Eight pro-Hadi fighters were also killed in fighting, they said.
AFP could not independently verify the death toll.
In other fighting, officials in Taez southwest of Sanaa said intense clashes had caused casualties, among them civilians.
Rebels fired mortar rounds at a public hospital in Taez, including at its intensive care unit, employees said.
Loud explosions were heard across the city, residents said.
An official said rebel shelling killed 13 civilians.
In the southern city of Daleh, coalition aircraft dropped medical aid to pro-Hadi fighters after the rebels prevented a humanitarian convoy from delivering aid, officials said.
Hadi supporters in Daleh province said Sunday they had killed 22 rebels in five ambushes.
The United Nations says millions of people have been affected by the conflict and are struggling to access health care, water, food and fuel.
It estimates that at least 551 of those killed since late March were civilians, including at least 115 children.