More than 140 Houthi fighters have been killed after Yemeni soldiers repelled an assault on the government's regional headquarters in the northern city of Saada, the army has said.

A military official said that the fighters launched their attack from three directions before dawn on Sunday.

"The army killed more than 140 rebels after thwarting an attempted attack on Saada," the official said, describing the fighting as "the fiercest" since the start of the military offensive on August 11.

The Houthis released a statement saying that the army's allegations were false and made to justify military offensives in residential areas in Saada.

The group did, however, say that fighting was continuing in a number of locations across Saada province, including the directorates of al-Malahid and Shada.

Separately, local sources said that about 150 fighters had been killed in al-Anad and al-Magash districts.

'Human shields'

Meanwhile, in an address to mark the Muslim Eid al-Fitr holiday, Ali Abdullah Saleh, Yemen's  president, said that the Houthi fighters were killing civilians and using some people as "human shields".

Last week dozens of civilians were reported killed in two army air raids, sparking condemnation from aid organisations and Yemeni rights groups.

"We hoped this offer would not be met with escalation including kidnapping, killing innocent citizens and using them as human shields," he said.

The government had said a permanent ceasefire would come into force on Saturday if the fighters accepted a series of conditions.

However, Abdul Malek al-Houthi, the fighters' senior commander, was quoted by Asharq Al-Awsat newspaper on Sunday as saying that the state was "not serious" in its truce offer.

"The government meant to use [the truce] for military purposes," al-Houthi said.

"If the government reviewed its stance and improved its behaviour and dealt with us as citizens who have rights, including the right to adhere to the teaching of Islam ... there would have been no problem." 

'Groundless accusations'

Al-Houthi also rebuffed government claims that his group is backed by Iran.

"These are groundless accusations," he said when asked whether his group, which consists of Shia Muslims from the Zaidi sect, was receiving moral and financial support.

The government said it halted its military operations on Friday night, but the Houthis said the army was "continuing their aggression in the combat zone despite announcing a suspension of hostilities."

In a statement, they said army attacks were "accompanied by intense rocket and
shellfire," comparing the fighting to "a state of war."

Five weeks of fighting has led to the unfolding of a humanitarian crisis among the tens of thousands of civilians forced to flee from their homes, according to relief groups.

The United Nations has estimated that about 150,000 people have been displaced by instability in Saada province since sporadic fighting broke out in 2004.