- Heavy fighting reported by residents despite UN-brokered truce
- Houthis hit by air raids in Sanaa, Taiz and Aden
- Residents report artillery exchanges between rival factions
- Both sides exchange blame over violence
Arab coalition air strikes and heavy shelling between warring factions shook several cities in Yemen, despite a UN humanitarian truce which took effect just before midnight.
Saturday's pause in the fighting was meant to last a week to allow aid deliveries to the country's 21 million, most of who are in need of humanitarian help.
Air raids pounded Houthi and Yemeni army units in the capital Sanaa and in the embattled southern cities of Taiz and Aden, where residents also reported intense artillery exchanges between the fighters and local militiamen, according to Reuters news agency.
In Aden, one of the country's most deprived and war-torn areas, witnesses said Houthi forces fired mortars and Katyusha rockets at opposition fighters based in northern areas and around the city's international airport.
Brigadier General Ahmed Asseri, a spokesman of the Saudi military which is leading the Arab coalition, earlier said the coalition needed to know that the Houthis would respect the truce and what the terms of breaching the agreement were.
Houthi leader Abdelmalik al-Houthi said the truce had to be conditional "on the commitment of the regime and their mercenaries".
Hakim al-Masmari, the editor-in-chief of the Yemen Post, told Al Jazeera that the people of Yemen always viewed the ceasefire as fragile.
"There have been numerous air strikes in numerous provinces. No one expected the ceasefire to succeed as Yemen is a lawless country, it's controlled by militants and not a government," Masmari said.
"It is a Yemeni version of a ceasefire, which means we're living in a lawless country or a country with no government."
Stephane Dujarric, the UN spokesman, on Friday said "it is imperative and urgent that humanitarian aid can reach all vulnerable people of Yemen unimpeded and through an unconditional humanitarian pause".
More than 80 percent of the country's 25 million people are believed to be in need of some form of emergency aid.
The announcement came shortly after the UN envoy to Yemen, Ismail Ould Cheikh Ahmed, wrapped up negotiations between the Houthi rebels and officials from the exiled government of President Abd-Rabbu Mansour Hadi in Sanaa.
Al Jazeera's Kristen Saloomey, reporting from the UN headquarters in New York, on Friday said that aid agencies were poised to move in as soon as the ceasefire was due to start.
Source: Al Jazeera and agencies