Fighting in Yemen, with government forces and their Saudi-led allies battling Houthi rebels backed by Iran, raged from Friday into Saturday on the Saudi-Yemen border, despite a 72-hour cease-fire that ended late Saturday.
Witnesses reported Saudi-led coalition airstrikes on Houthi missile launchers east of the capital, Sana'a.
All parties had agreed to honor the U.N.-backed truce as a means to allow critically needed supplies to reach civilians cut off from outside help.
U.N. special envoy Ismail Ould Cheikh Ahmed had described the truce as "largely holding" on Saturday and was seeking to extend it, but there was no information available on whether combatants would agree to such a move.
Ahmed described the cease-fire as an opportunity to establish a foundation for talks to end nearly two years of civil war in Yemen, which borders Saudi Arabia on the south. Monitors say nearly 7,000 people, at least half of them civilians, have died since the uprising began.
Late Friday, Ahmed met in the Saudi capital with exiled Yemen Vice President Ali Mohsen al-Ahmar, and said afterward that Yemeni government forces were "exercising restraint" in the face of what he said were more than 400 truce violations by Shi'ite rebel fighters.
The cease-fire was the sixth formal attempt to end the fighting since the Saudi-led Sunni coalition of Gulf states intervened early last year to support the internationally recognized Sunni government of President Abd Rabu Mansour Hadi.
Houthis launched their rebellion in 2014, after years of accusing the Sunni-led Sana'a government of widespread discrimination.