"This isn't a major surprise, because we know this is a very complex political landscape in Yemen.

"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."

Military operations halted

Earlier, 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.

in depth

 

  Listening Post: Media spotlight on Yemen
  Riz Khan: Yemen, a failed state?
  Video: Ceasefire holding
  Video: Yemen's tough al-Qaeda challenge
  Inside Story: Can the West save Yemen?
  Inside Story: Focus on Yemen's future
  Profile: Yemen's Houthi fighters

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

"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.

Our correspondent said the breakthrough was also in part due to Western pressure on Saleh to tackle Yemen's internal problems.

"It came when Ali Abdullah Saleh was asked by the international community during the London conference [held last month] to come up with a swift, radical solution to Yemen's pressing problems," Ahelbarra said.

"I think he decided to start first with the war in Saada, to give him more leeway - a window of opportunity - to tackle Yemen's most delicate problem, which is the secessionist movement in the south."

Yemen said last week it had handed the Houthi fighters a timetable for implementing the ceasefire terms, a week after rejecting a truce offer from the group because it did not include a promise to end hostilities with neighbouring Saudi Arabia.

Saudi connection

The kingdom was drawn into the conflict in November when the group seized some Saudi territory, complaining that Riyadh was letting Yemeni troops use its land for attacks against them.

Riyadh declared victory last month after the Houthis offered a separate truce and said they had withdrawn from Saudi territory.

Six-point agreement

  Houthis agree to:
  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

Yemeni officials have said that as part of a truce deal, Sanaa would allow Houthi representatives to sit on a committee overseeing the truce, and the group's fighters would hand over weapons they seized from Yemeni and Saudi forces.

Yemen state television said the government and the group had also formed four smaller committees to supervise the truce in four areas, including on the Yemen-Saudi border.

The deadline for the full implementation of the truce had been a point of contention, with the Houthis asking for more time for their fighters to leave mountainous positions, they said.

The Houthis say their community of Shia Muslims from the Zaydi sect suffer discrimination and neglect and that the Yemeni government has allowed Sunni conservatives influenced by the Saudi religious establishment too strong a voice in the country.

Led by Abdul-Malik al-Houthi, the brother of the movement's late leader, 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.