Arab coalition-led air strikes and ground fighting have been reported in Yemen, hours after a United Nations-brokered week-long truce was supposed to come into effect.
The air strikes early on Saturday in the capital Sanaa and the country's third-largest city of Taiz followed reports of ground fighting between Shia Houthi rebels and their rivals in Taiz, security officials told the Associated Press news agency.
Both sides blamed the other for breaking the ceasefire.
The United Nations announced the truce would start on Friday, July 10 at 23:59 local time and take effect until the end of Ramadan on July 17 so aid agencies could deliver urgently required humanitarian assistance.
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