Clashes also broke out Saturday in Algeria, as opposition activists there tried to copy the tactics of their Tunisian neighbours, who forced their longtime leader to flee the country more than a week ago.

The protests in Yemen appeared to be the first of their kind. The nation's 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-Qaida, 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.

AP