Yemen's army accused Shiite rebels of breaking a ceasefire yesterday, just hours after it came into force, saying they killed four soldiers in a string of attacks in the country's far north.

The head of military operations in Saada province, General Mohammed Abdullah al-Qussi, said he himself came under rebel attack.

"I escaped an assassination attempt by the rebels who opened fire on my car," General Qussi said.

"The rebels broke the ceasefire and carried out a series of attacks in Iqab district which resulted in dead and wounded among our troops," General Qussi added.

Another military source said three soldiers were killed in Iqab and a fourth in Al-Ain district, in the south of Saada province, where the rebels are based, and that several soldiers were wounded.

They were the first reports of violations of the ceasefire between the government and the rebels that came into force at midnight (2100 GMT Thursday) in a bid to end six years of on-off fighting.

There was no immediate comment from the rebels.

Earlier yesterday, army commanders had reported a halt to clashes across the rugged northern mountains after rebel leader Abdul Malak al-Huthi ordered his fighters to respect the truce announced by President Ali Abdullah Saleh.

"Calm reigns on all fronts from Saada and Malahidh (in the far north near the Saudi border) to Harf Sufian," further south, one field commander said.

Commanders had said they had seen rebel fighters start work on removing the roadblocks they have maintained on some of the trunk routes through the northern mountains blocking government traffic.

UN chief Ban Ki-moon welcomed the truce, his spokesman said yesterday. Mr Ban "hopes that the ceasefire will hold and that it will provide an opportunity to fully resolve this conflict," Martin Nesirky told a media briefing.

Mr Nesirky said the United Nations was still pressing for full access for humanitarian aid to be provided to displaced civilians estimated to number as many as 150,000.