The 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 correspondent added.

The massive deployment by Saleh loyalists came in response to an opposition call for an intensification of protests against his rule amid a deadlock in the political process in the face of the president's long absence abroad.

Saleh has been receiving medical treatment in neighbouring Saudi Arabia for wounds sustained in a June 3 bombing in his palace.

"We have called for intensifying the challenge in order to move towards a peaceful solution," said Huria Machhur, spokeswoman of 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 plan proposes that Saleh transfer power to the vice president within 30 days in exchange for a promise of immunity from prosecution.

Saleh vowed last month to return "soon" to his impoverished country.