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 U.N. 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.

Yemen's president is expected to appoint a new prime minister within 48 hours under a new deal with Shiite rebels in return for ending their weeks-long protests, a source close to the presidency said Thursday.

At least 12 people were killed in fierce overnight clashes between army-backed Yemeni tribes and Shiite Huthi rebels pressing a protest campaign against the government, tribal sources said on Saturday.

Fighting raged in Jawf province north of Sanaa as rebels sought to seize routes to the capital where their supporters have staged weeks of escalating protests against the central government.

Yemeni Shiite rebels and activists took to the streets of Sanaa Wednesday to reject a presidential overture to replace the government and reduce a disputed fuel price hike.

Faced with increased pressure from the Shiite rebels, who are also known as Huthis, and a deepening political crisis, President Abdrabuh Mansur Hadi announced the measures on Tuesday.

Rival protests stoked up tension in Yemeni capital Sanaa on Sunday as a presidential negotiating team abandoned talks with Shiite rebels, accusing them of seeking to ignite a war.

President Abdrabuh Mansur Hadi urged "vigilance and increased preparation to face any options that could be imposed" on Yemen, at a meeting with the supreme security and military committee, state news agency Saba reported.

Yemen's government put a draft proposal to rebels on forming a technocrat government Saturday, a spokesman said, as fears mount that a new wave of violence could hit the impoverished nation.

A presidential delegation handed the document to representatives of Shiite Huthi rebels, who have camped in their thousands around Sanaa this week, pressing the government to quit.

President Abdrabuh Mansur Hadi urged Yemen's armed forces Thursday to "raise their level of vigilance" on the eve of the expiry of a rebel deadline for the government to quit.

Thousands of armed Shiite rebels in Yemen strengthened their positions in the capital Sanaa on Wednesday as they pressed their campaign to force the government to resign, Agence France Presse correspondents witnessed.

The rebels have been fighting an off-conflict with government troops in the northern mountains for the past decade but analysts warned their bid for a greater share of power in a promised new federal Yemen was creating a potentially explosive situation.

Tens of thousands of people joined an anti-government rally in Sanaa on Monday in response to a call by Shiite rebel commander Abdulmalik al-Huthi, an Agence France Presse journalist reported.

The protesters assembled in Change Square before parading in the center of the capital, where supporters of the rebels, who are known as Huthis or Ansarullah, had converged during the morning after travelling from outside the city.

Fierce clashes broke out Saturday between pro-government tribesmen and Shiite Huthi rebels near the Yemeni capital, as the president vowed that authorities will not tolerate any violence.

The Huthis -- also known as Ansarullah -- have advanced from their northern mountain strongholds towards the capital in a suspected attempt to expand their sphere of influence as Yemen is reorganized into six regions.