Saudi-led warplanes bombarded Yemeni rebels at dawn Sunday, witnesses said, in a new blow to a UN-proposed truce in the impoverished country where millions are threatened with famine.
Air strikes hit the Shiite Huthi stronghold of Saada in Yemen's north, as well as other rebel positions south of the capital Sanaa and in the southern province of Lahj, residents said.
There were no immediate reports of any casualties.
The UN-proposed humanitarian truce technically went into effect at 2059 GMT Friday and is supposed to run until July 17, the last day of the holy Muslim fasting month of Ramadan.
But the ceasefire, much needed to rush food supplies to a population threatened by famine, has been flouted by strikes conducted by the Saudi-led coalition and fighting on the ground.
The ceasefire was declared after UN chief Ban Ki-moon received assurances from exiled Yemeni President Abedrabbo Mansour Hadi and the Huthis that it would be respected.
The coalition said it has not received a formal request from Hadi's government to observe a truce, while the rebels said before the ceasefire went into effect they had little hope it would succeed.
More than a week ago the United Nations declared Yemen a level-3 humanitarian emergency, the highest on its scale, with nearly half the country facing a food crisis.
More than 21.1 million people -- over 80 percent of Yemen's population -- need aid, with 13 million facing food shortages, while access to water has become difficult for 9.4 million people.
The UN says the conflict has killed more than 3,200 people, about half of them civilians, since late March.