A Yemeni supporter of the Shiite Huthi rebels stands guard during a celebratory rally after the anti-government movement seized key state installations, on September 26, 2014 in the capital SanaaA Yemeni supporter of the Shiite Huthi rebels stands guard during a celebratory rally after the anti-government movement seized key state installations, on September 26, 2014 in the capital Sanaa

Yemeni rebels who have overrun the capital clashed with presidential guards Saturday as they ignored a demand to leave the city following a UN-brokered peace accord.

Fighting erupted overnight after the Huthi Shiite rebels tried to occupy the home of the national security chief, according to witnesses.

Two fighters were killed in the gunfight which lasted around three hours, while 15 others were wounded and a number of insurgents were captured by presidential guards, rebel sources said.

Hours earlier President Abdrabuh Mansur Hadi had urged the rebels to leave the capital Sanaa, much of which they seized last week.

"Settling accounts by force and acts of vengeance will not build a state," Hadi said.

The rebels have swept from their stronghold in the rugged northwestern mountains to the capital demanding economic and political reforms.

They seized key state installations nearly a week ago, mostly in northern Sanaa, without any resistance after clashes on the city's outskirts with Islamists killed more than 270 people.

The presidential complex in southern Sanaa is said to be protected by four brigades deployed around the palace and in nearby hills.

The violence has added to instability in Yemen since an uprising that led to the ouster of autocratic president Ali Abdullah Saleh two years ago.

Washington last week ordered a cut in the number of American government staff in Yemen due to the "unpredictable" security situation.

- Troubled transition -

The peace deal, signed last Sunday, was aimed at putting the post-Saleh transition back on track in impoverished Yemen, which borders oil-rich Saudi Arabia and is a key US ally in the fight against Al-Qaeda.

The Huthi-linked Al-Masirah TV station said Saturday the rebels had also now signed a protocol stipulating they must hand over seized institutions and dismantle armed protest camps in and around Sanaa.

Also known as Ansarullah, they have battled the government for years from their heartland of Saada, complaining of marginalisation.

Analysts say that the rebels, who have also seized large areas north of Sanaa, want to establish themselves as the dominant political force in the north, in preparation for a planned federation.

The situation on the ground remained confused following the lightning takeover of Sanaa by the rebels.

Interior Minister Abdo al-Tarib earlier urged government forces not to confront the insurgents as they swept across the capital.

Sources close to the presidency have accused Saleh of collaborating with the rebels by using his clout among army chiefs.

Military sources said the rebels aimed to smoothly bring under their control army bases in Sanaa and other regions, by securing the cooperation of top officers.

On Friday Hadi appeared to refer to Saleh backers, saying: "We were let down by those who put their interests above those of the homeland."

Hadi has so far failed to name a new prime minister as stipulated by the agreement to end the fighting.

Yemeni authorities have repeatedly accused Iran of backing the rebels, who also appear influenced by Lebanon's powerful Shiite militia Hezbollah, which is supported by Tehran.

AFP