'Precarious calm'

A military source said that "the situation is calm on all fronts in Saada province", the centre of the six-year-old conflict.

"But the calm is precarious," said another.

in depth


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  Video: Ceasefire holding
  Inside Story: Focus on Yemen's future
  Profile: Yemen's Houthi fighters

Abdul-Malik al-Houthi, the leader of the Houthis, confirmed that there was no fighting, saying the "ceasefire is being respected and the situation is developing positively".  

Al Jazeera's Hashem Ahelbarra, reporting from Yemen's capital Sanaa, said the sporadic fighting on Friday was not unexpected, due to the complex political landscape in the country.

"This was not a war that was pitting the government against the Houthi rebels. You had also tribes fighting alongside the Houthis and tribes fighting with the Yemeni army.

"Definitely a ceasefire would never be able to mitigate the high tension in the northern part of Yemen."

The government had announced a halt to military operations on all fronts against the Houthis from the moment the truce went into force at midnight on Thursday.

Six conditions

Ali Abdullah Saleh, the Yemeni president, declared the ceasefire on Thursday night after the Houthis agreed to accept six conditions put forward by the government.

Six-point agreement

  Respect the ceasefire and open the roads
  Withdraw from regions they
have occupied
  Return captured weapons, ammunition and equipment
  Release civilian and
military detainees
  Respect the law and the
Yemeni constitution
  Pledge not to attack Saudi
Arabia's territory

"We have decided to halt military operations in the northwestern region ... to stop bloodshed, bring peace to the region," the president's office said in a statement.

The Houthis say their community of Shia Muslims from the Zaidi sect suffer discrimination and neglect and that the Yemeni government has allowed Sunni conservatives to wield too much influence.

The group has been in conflict with the government since 2004, but the fighting intensified last year.

Qatar brokered a short-lived ceasefire between the two sides in 2007 and a peace deal in 2008, but clashes soon broke out again.

Saleh unilaterally declared the war over in July 2008, but full-scale fighting resumed a year later.

The United Nations says 250,000 people have been displaced by the fighting.