Sana’a: Al Houthi rebels have begun withdrawing from positions they seized near the Yemeni capital under a truce agreed with armed tribesmen allied with the influential Salafist Al Islah (reform) party, officials say.

But some Al Houthi rebel fighters, known as Ansarullah, are refusing to evacuate positions they won after months of deadly battles despite an ultimatum by the army, tribal and military sources say.

The army meanwhile has deployed to prevent those who have left from returning to their positions, the military says.

President Abd Rabbo Mansour Hadi and Yemen’s main parties agreed last month to transform the unrest-riven country into a six-region federation as part of a political transition.

The rebels, whose northern region lacks any significant resources or access to the coast, believe the agreement will divide Yemen into rich and poor regions and have been trying to enlarge their zone of influence by pushing out from the mountains to areas closer to Sana’a.

As they advanced they seized areas in the northern province of Omran, leaving more than 150 people dead and overrunning the home base of the Al Ahmar clan which heads the powerful Hashid tribal confederation.

They then advanced to areas located only 15 kilometres from the capital.

Military sources said their objective was to capture Omran city and, from there, lay siege to Sana’a.

Their advance however was halted when the army and tribesmen joined forces and the rebels last week signed a truce with the tribesmen.

However implementation of the truce, which commits them to a ceasefire and to withdrawing their fighters from positions near Sana’a, has been slow.

On Monday, the head of the presidential commission overseeing the withdrawal of the fighters, Ali Ghashmi reported that the operation had finally started in Hamdan region, northwest of the capital.

“Elements from the military police and special forces began taking over positions evacuated by the rebels after the truce”, he told the official Saba news agency.

But a local government official said some fighters are refusing to budge.

“It is premature to say that all the fighters have left their positions,” the official said, adding that the process was further complicated due to “political interference”.

Al Houthis have been accused of collaborating with diehard supporters of former strongman Ali Abdullah Saleh, who was forced to resign in 2012 following a year-long uprising, in their push towards Sana’a.

Saleh’s critics accuse him of forming alliances with opponents of Yemen’s interim authorities, including Al Houthis, and hampering the deeply-tribal country’s political transition.