government protesters clashed with police blocking them from marching to Yemen's presidential palace in Sana'a Sunday, witnesses said. The clashes occurred while President Ali Abdullah Saleh and the main opposition group were preparing for talks that the government hoped would help avert an Egyptian-style revolt in the Arabian Peninsula state, a vital US ally against Al-Qaeda. “The Yemeni people want the fall of the regime,” protesters shouted during the demonstration attended by about 1,000 people, before dozens broke off to march to the palace. “A Yemeni revolution after the Egyptian revolution.” In the harshest response yet to a wave of protests in the capital, police prevented the smaller group from reaching the palace, hitting them with batons, while protesters threw rocks at the police, witnesses said. Four people were injured. Many of the Sana'a protests, including a “Day of Rage” on Feb. 3 attended by tens of thousands of opposition and pro-government demonstrators, ended peacefully. Although pro- and anti-government protesters have clashed in recent days, police have generally stayed out of the fray in Sana'a. They have clamped down more firmly outside the capital. Opposition officials said 10 protesters were briefly detained in Sana'a Sunday and 120 more were taken into custody overnight in the agricultural and industrial city of Taiz, where authorities broke up a demonstration Saturday. US-based Human Rights Watch criticized Yemen for allowing government supporters to assault, intimidate and sometimes clash with protesters calling on Saleh to quit, saying it raised concern about the government's respect for free assembly. Saleh, in power for more than three decades and concerned about unrest in some parts of the Arab world, said more than a week ago he would step down when his term ends in 2013 and pledged his son would not take over the reins of government. The offer, which included an invitation to dialogue among other concessions, was his boldest gambit yet to stave off a showdown with protesters in the poverty-stricken state, where about 40 percent live on less than $2 a day, while a third suffer from chronic hunger.