Arab League monitors have traveled to the Syrian flashpoint city of Homs as part of a mission to track promises by the government to withdraw its tanks and troops from cities and release political protesters.
The observers arrived Tuesday in Homs, where rights activists say government security forces had intensified their attacks in recent days and where some tanks were pulling back ahead of the monitors' visit.
The London-based Syrian Observatory for Human Rights said 20,000 protesters gathered in the city Tuesday, a day after security forces killed at least 30 people there.
Syrian television said the monitors were meeting with the governor of Homs.
The Arab League says observers from at least eight Arab countries will visit several other Syrian cities Tuesday, including Idlib, Hama and Daraa. Fifty monitors and 10 other league officials arrived in the country on Monday.
Rights activists and the opposition Syrian National Council say the government's agreement to the Arab League plan is a farce. Some anti-government protesters have criticized the league's stance to the point of accusing it of complicity in the killings.
Syrian National Council head Burhan Ghalioun called on the U.N. Security Council Monday to take over the international effort to stop the violence plaguing the country.
Activists and witnesses said government tanks and security forces ravaged Homs' Bab Amr district Monday with heavy shelling and gunfire. Amateur video posted on YouTube shows bodies lying in pools of blood in front of a house apparently struck by a shell. Another video shows tanks prowling the streets of the district, an army defector stronghold.
The Syrian Observatory for Human Rights said forces loyal to President Bashar al-Assad also opened fire on a protest in neighboring Hama province, killing three people. The group said four army defectors also were killed Monday by troops in a town near the Turkish border.
Activists say hundreds of people have been killed this month in attacks by Syrian security forces on civilians and in fighting between pro-Assad troops and army defectors. It is not possible to confirm casualty figures independently because Syria bars foreign journalists from operating freely.
Syria agreed to the Arab League plan under international pressure and threats of Arab sanctions. The plan requires Assad to give the monitors freedom of movement everywhere except sensitive military sites. Members of the team say they will avoid disclosing their travel plans in advance in order to maintain the element of surprise.
Syrian opposition activists have called on the observers to abandon the mission if the government blocks access to centers of anti-Assad protest such as Homs.
The United Nations estimates 5,000 people have been killed in violence linked to the uprising since it began in March. Syria says "armed terrorists" are driving the revolt. It accuses them of killing 2,000 security personnel during that period.