Dozens of activists calling for the ouster of Yemen's President Ali Abdullah Saleh clashed on Saturday with the regime's supporters in Sanaa, an AFP journalist reported.
Plainclothes police also attacked the demonstrators who marched to the Egyptian embassy in Sanaa chanting "Ali, leave leave" and "Tunisia left, Egypt after it and Yemen in the coming future."
The chants were referring to the ouster of veteran Tunisian strongman Zine El Abidine Ben Ali early this month and to continuing demonstrations against President Hosni Mubarak in Egypt, the biggest the country has seen in the three decades of his rule.
No casualties have been reported in the Yemen clashes.
A female activist, Tawakel Karman, who has led several protests in Sanaa during the past week, said that a member of the security forces in civilian clothes tried to attack her with a dagger and a shoe but was held by other protestors.
"We will continue until the fall of Ali Abdullah Saleh's regime," said Karman, who was granted parole on Monday after being held over her role in earlier protests calling for political change in Yemen.
"We have the Southern Movement in the south, the (Shiite) Huthi rebels in the north, and parliamentary opposition," all of which are calling for political change, said Karman.
Yemen, one of the poorest countries in the Arab world, faces a growing Al-Qaeda threat, a separatist movement in the south and a sporadic rebellion by Zaidi Shiite rebels in the north.
"But what's most important now is The Jasmine Revolution," said Karman, a journalist who is also a senior member of the opposition Islamist Al-Islah (Reform) party and heads a rights group, Women Journalists Without Chains.
Karman also called for Thursday, February 3 to be a "Day of Rage" throughout Yemen.
Protests have been taking place on a nearly daily basis in Sanaa since mid-January calling for an end to Saleh's rule which began in 1978.
Saleh was re-elected in September 2006 for a seven-year mandate.
A draft amendment of the constitution, under discussion in parliament despite opposition protests, could allow him -- if passed -- to remain in office for life.
Saleh had urged the opposition which rejected the amendment, to take part in April 27 parliamentary elections to avoid "political suicide."
The mandate of the current parliament was extended by two years to April under a February 2009 agreement between the ruling General People's Congress and opposition parties to allow dialogue on political reform.
The reforms on the table included a shift from a presidential regime to a proportional representation parliamentary system and further decentralisation of government -- measures that have not been implemented.
The dialogue has stalled, and a special committee set up to oversee reform has met only once.
Saleh is also accused of wanting to pass the reins of power in the impoverished Arabian Peninsula state to his eldest son Ahmed, who heads the elite Presidential Guard, an accusation he denies.