The protests come even as the U.S. has embarked on a plan to deepen its involvement in training the country's counterterrorism force to counteract a local affiliate of al-Qaida that has mounted several attacks against the U.S.
University students, rights activists and lawmakers marched Monday in the capital, Sanaa. Lawyers in black robes, led by their union chief, joined the demonstrators shouting slogans against the security forces and "the people want the regime to step down," a slogan mirroring those used in Egypt and Tunisia.
"A revolution of free opinion ... A revolution of freedom ... We should decide," shouted the protesters.
A counter-demonstration of at least a hundred government supporters holding up pictures of President Ali Abdullah Saleh confronted the protesters, shouting slogans against terrorism and supporting the government's call for dialogue.
The two groups scuffled in front of the university and three people were injured, two from stones and one was stabbed a traditional Yemeni dagger.
Police finally separated the two groups before the protesters marched toward the city center gathering steam as they went shouting, "Leave, Saleh."
Lawyer Hassan al-Dola said the anti-government protest was against "the widespread corruption and against the security apparatus that terrified the people."
"We will continue our protests until the regime falls," independent lawmaker Ahmed Hashid said.
Dozens of women, meanwhile, demonstrated outside of the police intelligence headquarters in the capital, calling for the release of their sons.
Local and international journalists also reported being attacked by police and government supporters and beaten.
Similar demonstrations took place in Aden and Taaz shouting, "Saleh, you are good in words but not in rule."
In Taaz, police dispersed demonstrators with tear gas and firing rounds in the air. Twelve people were injured and dozens arrested.
On Sunday, police armed with sticks and daggers on Sunday beat back thousands of protesters marching through the Sanaa. The protests have mushroomed since crowds gathered Friday to celebrate the ouster of Egyptian President Hosni Mubarak after an 18-day revolt fueled by similar grievances. Yemen is one of several countries in the Middle East feeling the aftershocks of pro-reform uprisings in Egypt and Tunisia.
Human Rights Watch said police on Sunday used electroshock tasers and batons to disperse protesters.
There were several checkpoints at streets leading to the presidential palace and some were blocked with barbed wire.
Sanaa state television said Sunday that because of the current situation in the region, Saleh, after he met with the U.S. ambassador to Yemen, canceled his visit to the United States scheduled for the end of this month.
Instead the president was reported to be visiting tribal areas around the capital to convince the powerful tribesmen not to join the protests.
Ties between the U.S. and Saleh have been growing lately over rising alarm in Washington about the activities of al-Qaida in the Arabian Peninsula
The U.S. military will begin a new training program with Yemen's counterterrorism unit, marking the first time the U.S. has trained the counterterrorism unit, which has traditionally focused on protecting Yemen's capital, according to a senior U.S. defense official. Under the plan, the training would begin in the next few months, and the Yemenis could more than double the size of their counterterror force, which now numbers about 300.
The official spoke on condition of anonymity because details are still being worked out.
The plans come as the U.S. watched rippling public unrest rattle many of its Middle Eastern allies, including autocratic leaders such as Egypt's former President Hosni Mubarak, who stepped down Friday.
So far, U.S. defense officials said there has been no impact on U.S.-Yemen military cooperation as a result of the public protests, and that Yemen remains committed to its operations against AQAP.
The new training program in Yemen will cost about $75 million, the defense official said. And the goal is to create a national counterterror unit that will be better able and equipped to travel out to tribal regions and ferret out insurgents hiding there.