In Tunisia, protests continued. Thousands of people rallied, calling on their new government to quit as the Prime Minister, Mohamed Ghannouchi, said he would resign only when the first democratic vote since independence has been held.

Demonstrators in Tunis were joined by hundreds of members of the police, discredited because of the bloody crackdown on protests against president Zine al-Abidine Ben Ali that ultimately led to his removal.

The protests in Yemen appeared to be the first of their kind. Its 23 million citizens have many grievances: they are the poorest people in the Arab world, the government is widely seen as corrupt and is reviled for its alliance with the US in fighting al-Qaeda, there are few political freedoms and the country is rapidly running out of water.

Still, calling for President Ali Abdullah Saleh to step down had been a red line that few dissenters dared to test.

In a reflection of the tight grip Mr Saleh's government and its forces have in the capital, Saturday's demonstration did not take place in the streets, but was confined to the grounds of the University of Sanaa.

About 2500 students, activists and opposition groups gathered there and chanted slogans against the President, likening him to the ousted Tunisian leader.

''Get out, get out, Ali. Join your friend Ben Ali,'' the crowds chanted.

Police fired tear gas at the demonstrators, whose grievances include proposed constitutional changes that would allow the President to rule for a lifetime.

Yesterday there were more calls for change by dozens of students protesting outside Sanaa University. Witnesses said clashes broke out as security forces tried to disperse them. Al-Jazeera television said one of its cameramen was beaten by police.

Also yesterday, about 200 journalists marched in Sanaa to demand the release of a press freedom activist, Tawakel Karman, who was arrested on Saturday, and other detainees.

Protests were also held in the southern port city of Aden. Police fired on demonstrators, injuring four, and detained 22 others in heavy clashes.

In Algeria, riot police armed with batons and shields clashed with rock- and chair-throwing protesters who tried to march in the capital in defiance of a ban. An opposition party official said more than 40 people were injured.

In Saudi Arabia, a local man died in what appeared to be the kingdom's first case of self-immolation since an unemployed man set himself on fire in Tunisia last month, sparking the riots that brought down its government.