Tens of thousands of demonstrators, some chanting "down, down with the regime," today marched in several towns and cities in Yemen against the country's autocratic president, a key US ally in the fight against Islamic militants.
Police opened fire and tear gas to break up one of the marches, witnesses said.
Security officials confirmed a demonstrator was critically wounded by police fire. Two others were also hurt in the eastern town of Mukalla.
In the capital of Sanaa, scuffles and stone-throwing briefly erupted between thousands of anti-government demonstrators and supporters of President Ali Abdullah Saleh. However, police stepped in and there were no reports of injuries.
There was a heavy security presence around the Interior Ministry and the Central Bank. Military helicopters hovered in some areas.
Anti-government protests have erupted in other Arab countries including Tunisia and Egypt in recent weeks.
In Yemen, protests erupted in several towns after Saleh sought to defuse demands for his removal by pledging not to seek another term in 2013 and not to let his son inherit power.
Anti-government protesters said they don't trust Saleh and demanded that he quit immediately.
Supporters of the president carried banners warning that the opposition was trying to destabilise Yemen.
The United States has taken a sharp tone on Egypt, urging Mubarak to move swiftly on democratic reform. But it cautiously praised reform pledges in Yemen. State Department spokesman P J Crowley has welcomed Saleh's "positive statements."
In Yemen, where the population is overwhelmingly very young, unemployment is 35 % and poverty is endemic. About 40 % of the population lives on less than 2 dollars (£1.30) a day.