Police opened fire and tear gas to break up one of the marches, witnesses said, and security officials confirmed a demonstrator was critically wounded by police fire. Two others were also hurt in the eastern town of Mukalla, but further details were not immediately available.

In the capital of Sanaa, scuffles and stone-throwing briefly erupted between thousands of anti-government demonstrators and supporters of 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.

Protests erupted in several towns after Saleh sought to defuse demands for his ouster by pledging Wednesday 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. "Thirty years of promises and thirty years of lies," read a banner raised by marchers in Sanaa.

Supporters of the president carried banners warning that the opposition was trying to destabilize Yemen.

Mohammed Al-Sabri, spokesman for a coalition of opposition groups, said hundreds of thousands took to the streets Thursday. He said the opposition is ready to engage in a dialogue with the president, but want concrete proposals for change.

"We welcome this decision, but if the people want the president to leave, we will adopt their demand," Al-Sabri said. "We have had political demands which we discussed with the regime for the past three years, but unfortunately failed." He said peaceful protests would continue for the next three months.

In Brussels, Yemeni Foreign Minister Abu Bakr Al-Qirbi warned that outside interference — he mentioned Iraq, Afghanistan or Pakistan — would be counterproductive.

He said frustration of the young generation was widespread across the Arab world, including in his country. "I think the frustrations of younger generations are universal in the Arab world," Al-Qirbi told The Associated Press in Brussels, where he had come to seek development aid.