An influential cleric and former mentor of Osama bin Laden has joined tens of thousands of Yemeni opposition activists and called for the government’s replacement with an Islamic state.

Sheik Abdul Majid al-Zindani Tuesday praised the anti-government protesters and called for President Ali Abdullah Saleh to step down. Zindani said the Yemeni president had come to power by force and that “the only way to remove him is through the “force of the people.”

The New York Times reported that Zindani, whose word carries considerable weight in Yemen, was guarded by his private security force of 10 men carrying AK-47 assault rifles.

The controversial cleric has been listed as a terrorist by the U.S. since 2004, suspected of fund-raising for al-Qaida and other groups. In the past, Zindani has maintained ties with Mr. Saleh. Until two weeks ago, he had backed the idea of the Yemeni president staying in power until his term ends in 2013.

Zindani’s appearance came as Mr. Saleh accused his ally, the United States, for the first time, of fueling the daily protests against him. In an unusual display of anti-American sentiment, Mr. Saleh said the U.S. and Israel have been working together to foment unrest designed to destabilize the Arab world. He said the alleged plot had been orchestrated in Tel Aviv under U.S. supervision.

U.S. State Department spokesman P.J. Crowley said on the social networking websiteTwitter Tuesday that Mr. Saleh “knows better” than to think the protests in Yemen are part of “external conspiracies.” He added that the Yemeni people deserve a better response from their leader.

Mr. Saleh has cooperated with Washington in recent years in fighting al-Qaida militants who have used lawless parts of his impoverished nation to plot attacks against the U.S. and its allies.

Shortly after the president’s comments, opposition activists gathered in a square near Sana’a University, chanting anti-Saleh slogans and protesting the killing of at least 24 people by Saleh loyalists since anti-government protests erupted in the country last month. Anti-government protests also took place in cities including Taiz and Aden, where demonstrators carried black flags in memory of those killed in the uprising.

Tuesday’s protests were backed for the first time by a coalition of opposition parties who on Monday rejected a proposal from Mr. Saleh to form a unity government. At least 1,000 demonstrators are now permanently camped out on the streets of Sana’a.

Meanwhile, President Saleh fired five of the country’s 22 provincial governors on Tuesday. The Associated Press quotes a government official as saying at least three were let go for criticizing Mr. Saleh’s crackdown on opposition protesters.