A three-day conference on the Yemen crisis has ended in Riyadh, with participants reiterating their support for exiled President Abd-Rabbu Mansour Hadi and the Arab coalition taking part in the ongoing air campaign.

The conclusion of the summit on Tuesday came as coalition jets hit Houthi fighters and their allies in Sanaa in the first strikes on the capital since the end of a five-day humanitarian truce on Sunday night.

Residents of Sanaa told the Associated Press news agency that the overnight strikes were the heaviest since the truce expired.

In Riyadh, Yemeni political and tribal figures concluded their meeting by agreeing to a joint statement which, along with supporting Hadi, called for the creation of a joint Arab force to secure cities in Yemen.

It also called for the implementation of a UN resolution which calls for the Houthis to withdraw from areas it has secured.

"This will pave the way and lay a solid foundation for resolving all the issues," Hadi said at the end of the conference, adding that the Houthis had failed to meet the conditions of the recent pause in fighting.

"The Houthi militias and the forces loyal to [former President Ali Abdullah Saleh] have misread the concept of the truce and this was reflected in the continued violations of the truce.

"They continued to destroy and kill, preventing the relief aid from being delivered to the people."

The Houthis boycotted the Riyadh summit, saying they would not attend talks in Saudi Arabia or any other country involved in bombing Yemen.

The latest Arab coalition air strikes hit the presidential palace complex and several bases of troops loyal to Saleh in Sanaa, Reuters news agency said.

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Witnesses said the targets included the Republican Guard missile brigade base of Fajj Attan, in south Sanaa, where previous air strikes on April 20 set off a chain of explosions that killed 38 civilians.

Coalition aircraft also hit air defence and coastguard bases in Hodeida province on the Red Sea coast, witnesses told Reuters.

Residents also reported raids in the central province of Taez, and Daleh and Aden in the south.

The Houthi fighters and their allies have taken control of large parts of Yemen, including Sanaa, and were advancing on Hadi's southern stronghold of Aden when the coalition launched the campaign on March 26.

The UN said on Tuesday that about 1,850 people had been killed and more than 500,000 have been displaced as a result of the conflict raging in Yemen since late March.

Ban Ki-moon, UN secretary-general, has voiced his disappointment at the Yemeni combatants' failure to extend the humanitarian ceasefire.