Two people were killed in Yemen's southern city of Aden on Friday in protests against the 32-year rule of President Ali Abdullah Saleh, while loyalists and opponents held large rival rallies in the capital.
Protesters outside Sanaa University, repeating slogans which have echoed around the Arab world since the uprisings in Egypt and Tunisia, chanted: The people demand the downfall of the regime.
About 4 km (2.5 miles) across the capital, loyalists shouted support for a leader they said was holding the fractured and impoverished tribal nation together. The creator of unity is in our hearts. We will not abandon him, they chanted.
In Aden, more than 10,000 people took to the streets in several districts of the southern port city. Thirty-four people were wounded, mostly by live bullets, in the demonstrations that started after Friday prayers, witnesses said. One of the wounded was in critical condition.
Nineteen people have been killed in the past nine days in a sustained wave of countrywide anti-Saleh protests galvanised by the fall of the Tunisian and Egyptian presidents. Saleh has said he will not give in to anarchy and killing.
A U.S. ally against the Yemen-based al Qaeda wing that has launched attacks at home and abroad, the Yemeni leader is struggling to end protests flaring across the Arabian Peninsula's poorest state.
He is also trying to maintain a shaky truce with northern Shi'ite Muslim rebels and contain a secessionist insurgency in the south against northern rule.
In the city of Taiz, 200 km (125 miles) south of the capital, about 10,000 people staged an anti-government protest.
In Aden's Mansoura district, protesters stormed a city council building and set fire to a government vehicle parked outside the building.
THE REVOLUTION HAS STARTED
Outside Sanaa university, Saleh's opponents held an auction to raise money for their campaign, selling a car and a watch, which fetched 600,000 riyals ($3,000).
The revolution has started. It will not stop until all of our demands are met, said Fouad Dahaba, an opposition member of parliament who attended the rally. We are not less than the people of Tunis and Egypt, who were emancipated.
Saleh supporters in Tahrir Square in Sanaa, many of whom arrived in buses from provinces outside the capital, chanted Yes to stability, no to chaos.
There is no use in trying to destroy the country and divide it. We all must enter a dialogue to preserve the national interest, said Mohammad Saleh.
Authorities stepped up security in Sanaa before the rallies. An Interior Ministry statement late on Thursday ordered security forces to raise their security vigilance and take all measures to control any terrorist elements who might take advantage of the protests to infiltrate Sanaa.
Pro-Saleh loyalists wielding clubs and daggers have often sought to break up opposition protests in Sanaa and elsewhere.
Saleh has promised to step down when his term ends in 2013 and not hand power to his son, though he has backed out of similar pledges in the past.
State news agency Saba said on Thursday Saleh has assigned a committee headed by Prime Minister Ali Mohammed Megawar to open a dialogue with protesters to hear their demands.
Nine members of parliament resigned from Saleh's ruling party on Wednesday in protest against what they said was government violence against protesters, but the president still has the support of around 80 percent of parliamentarians.