Protesters march in Bahrain, Jordan, Yemen, and Egypt

Thousands chanted that they will not leave until Prime Minister Ahmed Shafiq, one of the Mubarak-era holdovers, is removed from office. Some waved flags of Libya to show support for the uprising next door.

“We made Mubarak step down, and we must make Shafiq also step down,’’ said Safwat Hegazy, a protester from the Muslim Brotherhood, Egypt’s largest opposition group.

Since Mubarak’s fall, military rulers have disbanded both houses of Parliament and promised constitutional reforms that will allow wider participation in elections, to be held within six months. They also promised to repeal emergency laws that give security forces largely unchecked powers, though only when conditions permit — a caveat that worries protesters.

In Bahrain, the first Persian Gulf state to be thrown into turmoil by the Arab world’s wave of change, tens of thousands rallying in the central square demanded sweeping political concessions from the ruling monarch.

Security forces made no attempt to halt the marchers, an apparent sign that Bahrain’s rulers do not want more bloodshed denunciations from their Western allies. In the early stage of the two-week-old rallies, troops had used lethal force.

The unrest is highly significant for Washington. Bahrain is home to the US Navy’s Fifth Fleet, which is the Pentagon’s main counterweight against Iran’s widening military ambitions. Bahrain’s Sunni monarchy, meanwhile, is under pressure from Saudi Arabia and other Gulf rulers not to yield to the Shi’ite-led protesters, fearing it could open footholds for Shi’ite powerhouse Iran.

In the Arab world’s poorest country, Yemen, tens of thousands marching in the capital of Sana demanded that their US-backed president, Ali Abdullah Saleh, step down. It was one of the largest crowds since protests erupted earlier this month.

A Muslim preacher who led yesterday’s prayer told protesters it was their religious duty to topple Saleh, describing him as a “devil who has driven us to the stone ages.’’