Yemeni President Ali Abdullah Saleh has urged his security forces to protect the demonstrators who are calling for him to resign.
Yemen's state-run Saba news agency published a statement saying Saleh ordered the security forces to prevent any clashes between pro- and anti-government protesters.
He also urged both sides to take precautions against those who may try to infiltrate the protests and incite violence.
On Wednesday, thousands of anti-government protesters streamed into a square in Yemen's capital, Sana'a.
The opposition protesters gathered near Sana'a University, where at least one person was killed and 12 injured late Tuesday. The clash took place when attackers using guns and other weapons tried to disperse protesters who have been camping out at the site for days.
The violence brings the number of people killed in Yemen since demonstrations began this month to at least 12.
At least seven members of parliament submitted their resignations from the ruling party Wednesday to protest the government's violent response to the demonstrations. They said they would form an independent bloc in the legislature.
Protests challenging Saleh's 32-year rule took place in other parts of the country Wednesday. Demonstrators and security force members clashed in the port city of Aden. Also, thousands of chanting anti-government demonstrators marched through the eastern city of al-Mukalla.
Some information for this report was provided by AP and AFP.