Anti-government protesters have staged regular demonstrations in Sanaa for months [REUTERS]

Troops loyal to Yemeni President Ali Abdullah Saleh have deployed in force in Sanaa, the capital, after opposition groups called new mass demonstrations demanding an end to his decades-long rule.

Security forces closed off all access to the capital from Saturday afternoon while armed civilians loyal to the president also took to the streets.

The massive deployment came in response to an opposition call for an intensification of protests with the political situation in the country unresolved since Saleh left the country in June for medical treatment in Saudi Arabia after being wounded in an attack on his palace.

"We have called for intensifying the challenge in order to move towards a peaceful solution," said Huria Machhur, spokeswoman for the opposition National Council, an umbrella group of anti-Saleh forces.

"The political process has reached an impasse because of Saleh's refusal to sign the Gulf plan," she said, adding that popular protests which began in January should continue "until the fall of the regime."

The Gulf Co-operation Council plan stated that Saleh transfer power to the vice-president within 30 days in exchange for a promise of immunity from prosecution.

Saleh has been vowing to return to Yemen "soon" for several weeks.

Meanwhile, a suicide bomber killed four soldiers in southern Yemen when he detonated his car at a checkpoint on Saturday.

An official said the suicide bomber drove up to the checkpoint on the road between the city of Aden and Abyan province. Ten peolpe were also wounded.

Five people were also killed in the Zinjibar area on Saturday in clashes with the army.

Source: Al Jazeera and agencies