Photo: A humanitarian crisis is escalating across Yemen as fighting prevents the delivery of aid supplies

Scattered clashes between rebels and pro-government forces in Yemen have undermined a UN-brokered ceasefire aimed at facilitating the delivery of much-needed humanitarian supplies in the war-devastated country.

At least 11 people were killed on the first day of the ceasefire, which - despite sporadic attacks - was largely holding across the country after taking effect shortly before midnight on Wednesday.

Both sides blamed the other for breaching the 72-hour truce.

At least 10,000 people have been killed - more than half of them civilians - in the conflict while another three million are displaced and millions more need food aid.

The government of President Abd-Rabbu Mansour Hadi, backed by a Saudi-led Arab coalition, said on Thursday that Iranian-allied Houthi rebels shelled the strategic city of Taiz, which is held by pro-government forces.

"Taiz suffered heavy shelling ... and the siege of it by the Houthis has continued," Yemeni General Samir Haj was quoted as saying by the state news agency Saba.

Meanwhile, a Houthi-run news agency said its fighters had repelled attacks by government forces in the northwestern al-Jawf province in the early hours of the truce.

The deaths on Thursday included three civilians killed in a coalition air raid on Saada province, a Houthi stronghold, according to rebel-controlled media.

Five pro-government fighters were killed in two rebel attacks in Saada and Hajja provinces, according to pro-government forces, while three rebels were said to have died in attacks in the Red Sea province of Hodeida.

A man and his daughter were also wounded in a cross-border attack from Yemen on the kingdom's Jazan region, according to Saudi civil defence authorities.

A Saudi-led coalition intervened in March 2015 to support pro-government forces after Houthi rebels overran much of the country.

Saudi Arabia and the United States accuse Iran of arming fighters allied with forces loyal to ex-president Ali Abdullah Saleh, charges Tehran denies.

Both sides declared respect for the ceasefire but reserved the right to respond to infractions.

The coalition has said it will continue an air and maritime embargo to prevent weapons shipments to the rebels, and will maintain airborne reconnaissance.

At dawn, coalition aircraft flew twice over the rebel-held capital, Sanaa, without conducting raids, according to residents, who said they have had enough of failed truces.
'Mocking us'

"They're mocking us with a three-day truce," said Ali al-Doush, a 32-year-old civil servant who has not been paid for three months. "We want an end to the war.

EU foreign policy chief Federica Mogherini late on Wednesday said the truce should be a first step towards resuming UN-led peace talks, urging all parties in the conflict to respect it.
The ceasefire will allow urgent humanitarian assistance to reach large parts of the population that have suffered drastic shortages in basic needs such as food and medical supplies, she said.

The last ceasefire attempt began in April and collapsed as UN-brokered peace talks broke down in August.

The UN's humanitarian coordinator for Yemen, Jamie McGoldrick, on Wednesday told reporters he hoped the truce will provide a chance for aid workers to reach areas isolated by the fighting.

"We're seeing very high levels of malnutrition and food insecurity," he said. Al-Jazeera