Yemeni rebels camped out across the capital for weeks seeking greater political clout clashed with pro-government tribesmen Tuesday, leaving 11 people dead, a tribal source said.
It came as a UN envoy pressed efforts to broker a deal to end demonstrations that have seen tens of thousands of Shiite rebels overrun Sanaa, cutting road links to the provinces.
The fighting erupted near a new protest camp close to an army barracks in Hamdan on the northern outskirts of the capital, the tribal source said.
Nine loyalist tribesmen and two rebels were killed. Islamist militiamen of the Islah party joined the fighting on the side of the tribesmen.
President Abdrabuh Mansur Hadi has agreed to involve the rebels in the formation of a new government to replace the unpopular administration which imposed austerity measures -- including a sharp fuel price increase -- earlier this year.
But the rebels are also demanding positions in key state institutions, and UN special envoy to Yemen Jamal Benomar has been shuttling between the two sides to firm up the details of a deal.
The Hamdan camp is the eighth armed protest camp the rebels have set up in the Sanaa region since they launched their campaign on August 18.
It was the second day in a row rebel activists have clashed with loyalist tribesmen. On Monday, there was heavy fighting in Jawf province, northeast of the capital.
The rebels have waged an on-off insurgency in the northern highlands since 2004.
They have taken advantage of shifting alliances among the region's Zaidi Shiite tribes since veteran strongman Ali Abdullah Saleh was forced from power in 2012 to lay claim to a share of power in Sanaa.
The Zaidis are a minority in mainly Sunni Yemen but are the majority community in the northern highlands, including the Sanaa region.
The rebels, known as Huthis from the name of their leading family, are opposed by Sunni militants, including Al-Qaeda loyalists, as well as by some Zaidi tribes.
Their protest campaign has exacerbated an already difficult transition since Saleh's ouster, which has also seen mounting secessionist sentiment in the formerly independent south and persistent attacks on the security forces by Al-Qaeda.