Yemen's opposition on Monday rejected a Gulf initiative for President Ali Abdullah Saleh to step down because it appears to offer him immunity from prosecution, while Saleh himself welcomed it.

Gulf foreign ministers meeting in Riyadh late on Sunday said publicly for the first time that the framework of their mediation effort involved Saleh standing down, though it did not say when that could be.

The ministers called for a meeting of parties to the Yemeni conflict to meet in Saudi Arabia, but did not set a date.

"Who would be a fool to offer guarantees to a regime that kills peaceful protesters? Our principal demand is that Saleh leaves first," opposition spokesman Mohammed Al-Sabry said, referring to assurances that Saleh and his sons would not face the fate of rulers in Tunisia and Egypt.

Tens of thousands filled the streets of Sanaa, Taiz, Hudaida, Ibb and the southeastern province of Hadramau to protest against the GCC plan on Monday, witnesses said.

Diplomatic sources say Saleh has dragged his heels for weeks over US attempts to get him to agree to step down and end protests crippling the country since early February, manoeuvring to win guarantees that he and his sons do not face prosecution.    

With more than 100 protesters killed as security forces try to break up the demonstrations with tear gas and live fire, activists have said they want to see legal action against Saleh and his sons, who occupy key security and political posts.

A spokesman for General Ali Mohsen, a Saleh kinsman whose units are protecting protesters in Sanaa, said on Monday that he welcomed the details of the GCC plan announced in Riyadh.

Shortly after the opposition rejected the Gulf initiative, Saleh's office issued a statement saying he accepted it.

"The presidency welcomes the efforts of our brothers in the Gulf Cooperation Council to solve the current crisis in Yemen," the statement said from his office said.

"He (Saleh) has no reservations about transferring power peacefully within the framework of the constitution," it added, in language Saleh has used before to argue he should oversee a transition involving new elections.

Long regarded by the West as a vital ally against Al Qaeda militants, Saleh has warned of civil war and the break-up of Yemen if he is forced to leave power before organising  parliamentary and presidential polls over the next year.

Saleh had sought Saudi mediation for some weeks, but Gulf diplomatic sources have said Riyadh was prompted in the end by concern over deteriorating security in its southern neighbour after Saleh failed to act on the backroom deal struck with US
officials on a quick exit.

Saudi Arabia, the world's biggest oil exporter, is the key financier of the Yemeni government as well as many Yemeni tribes on its border. Countries of the region became convinced that Saleh is an obstacle to stability in a country that overlooks a shipping lane where over 3 million barrels of oil pass daily.

The GCC statement on Sunday talked of "the formation of a national unity government under the leadership of the opposition which has the right to form committees ... to draw up a constitution and hold elections".   

It said Saleh should hand his authorities over to his vice president and that all parties should "stop all forms of revenge .. and (legal) pursuance, through guarantees offered" -- wording that appeared to offer Saleh assurances of no prosecution for him or his family once he leaves office.
   
Saleh's deputy, Abd-Rabbu Mansour Hadi, has said he is not interested, which could open the way to the perennial survivor nominating an interim successor of his own choice.

Even before the protests, Saleh was struggling to quell a separatist rebellion in the south and a Shi'ite Muslim insurgency in the north -- violence that has given the Arabian Peninsula branch of Al Qaeda more room to operate. - Reuters