Shia Houthi rebels have clashed with government forces in a Sanaa suburb as Yemen is at its most critical point since the revolution in 2011.

A gunfight broke out in the Sabaha district on Wednesday where Houthi protesters have been camping for weeks in a campaign to bring down the government and secure greater representation in state institutions.

Speaking from Sanaa, Al Jazeera's Hashem Ahelbarra said, "There is a great deal of anxiety and tension about what could happen in the coming days.

"People are asking whether it is going to be a short military confrontation or a protracted civil war - militias could join the government to fight the Houthis."

RELATED: Yemen's president faces political stalemate

On Tuesday, protest organisers said seven activists were shot dead as Houthis marched on government headquarters, while thousands blocked main thoroughfares in central Sanaa.

And troops in Hiziaz, a southern entrance to Sanaa, clashed with rebels who tried to drive a vehicle loaded with arms into the capital.

A civilian was killed and 15 others wounded in the confrontation, Yemen's top security commission said, adding that several police and soldiers were also wounded.

It accused rebels of firing machine guns and rocket-propelled grenades.

The rebels have so far rejected overtures from President Abd-Rabbu Mansour Hadi, who has offered to name a new prime minister and reduced a disputed fuel price hike.

Both concessions were core demands of the Houthis who launched their protests on August 18, after battling forces loyal to the government for months for control of key cities north of Sanaa.

Analysts say the rebels are trying to establish themselves as the top political force in the northern highlands, bordering Saudi Arabia, where Shia Muslims are the majority.