BEIRUT: Syrian security forces arrested more than 20 people, a rights group said Saturday, after thousands marched in pro-democracy protests in unrest that has posed the gravest challenge to President Bashar Al-Assad's rule. The Syrian Observatory for Human Rights named 21 people who had been rounded up by Syrian security in the southern city of Deraa, where the unrest first flared two weeks ago, and in Homs to the north of the capital. “It is assumed their arrests are as a result of the last protests,” the rights group said in a statement. “(The rights group) demands that the Syrian authorities release all detainees of opinion and conscience and to stop the practice of arbitrary arrests against political opposition and civil and human rights activists.” Thousands took to the streets in major cities after Friday prayers, defying security forces who fired tear gas and live ammunition and used batons to try and disperse protesters who have dismissed a limited reform gesture by Assad, in power for the last 11 years. Witnesses said security forces killed at least three protesters in the Damascus suburb of Douma on Friday, raising to over 60 the number of deaths in protests that were inspired by popular uprisings that have swept the Arab world. The United States, which has designated Syria as a “state sponsor of terrorism” since 1979, and the United Nations, condemned the latest escalation in violence. “Violence is not the answer to the grievances of the Syrian people,” Jay Carney, spokesman for US President Barack Obama, said in a statement. An official source said via state news agency SANA that “armed groups” were responsible for the violence in Douma, Homs and Deraa, where unrest came to a head after police detained more than a dozen schoolchildren for scrawling graffiti inspired by popular uprisings in the Arab world. MP criticizes forces A Syrian member of parliament for Daraa has denounced security forces for opening fire on his constituents “without pity” and has criticized President Bashar Al-Assad for not offering his condolences. In a video uploaded to YouTube, Yusef Abu Rumiyeh, addressing parliament, held the Daraa head of the security services responsible for the killings of demonstrators in the flashpoint southern town. YouTube indicated 74-year-old Rumiyeh's speech was made on March 27, when MPs invited Assad to present his promised reform package to parliament, which he did three days later.