Aden: Hours into a UN-brokered truce on Monday, Yemeni citizens reported heavy artillery fire, gun battles and air strikes in several parts of the country.
The ceasefire is meant to allow the start of peace talks in a country where fighting has killed more than 6,200 Yemenis and displaced millions.
The capital Sanaa spent a rare night without air strikes but air assaults by a Saudi-led coalition of Arab countries continued in at least three other parts of the country, residents said.
"There's continuous shelling in the downtown and the suburbs and we can hear explosions across the city," said Jameel Abdo Ahmed, a civil servant in the battered frontline city of Taiz.
Another resident said: "Nothing's changed."
The Saudi-backed government, which was forced out of Sanaa by Houthi fighters in 2014, and Houthi adversaries blamed each other for violence in Taiz, and Saudi-owned Al Arabiya TV accused the Houthis of launching a ballistic missile, in violation of the truce.
The Soviet-era Tochka missile was fired into the battle-scarred northern desert province of Al Jawf but was intercepted mid-air, the network reported.
Residents said there were air attacks in support of government forces in the provinces of Taiz, Al Jawf and on the outskirts of Sanaa.
A spokesman for the Saudi-led coalition did not immediately respond to a request for comment on the reports of continued air strikes.
The Houthi-run Yemeni state news agency Saba quoted a Yemeni military official saying: "the mercenaries did not abide by the ceasefire."
The UN-sponsored peace talks are set to begin on April 18 in Kuwait, bringing together the Houthis and the government they pushed out in what they said was a revolution against corruption.
Saudi Arabia and its allies began a military campaign in March last year aimed at preventing the Houthis and forces loyal to ex-President Ali Abdullah Saleh taking control of the country.
The Saudi-led coalition expelled enemy fighters from the southern port city of Aden in July but Houthi forces continue to hold the capital and tracts of the country, with the help of Saleh loyalists.
The United Nations special envoy for Yemen said a committee of military representatives from both sides would work to make the truce hold.
"Now is the time to step back from the brink," Ismail Ould Cheikh Ahmed said.
The truce terms included commitments for unhindered access for relief aid. Nearly half of Yemen's 22 provinces are on the verge of famine, the UN World Food Programme has said.
Yemen's foreign minister, Abdel Malek Al Mekhlafi, told Al Arabiya TV: "This truce is in its early stages, violations may occur in the beginning, but we hope the next few hours will see more discipline towards the ceasefire."