(CNN) -- Violence flared in Syria on Saturday, leaving at least 28 people dead, activists said.
The Arab League condemned the violence and warned of a crisis in the region if the Syrian government does not comply with an agreement made Wednesday with the group to "stop all violence" and allow outside observers into the country.
Opposition groups reported explosions, shelling, and heavy machine-gun fire Saturday in the western Syrian city of Homs, a hotbed of anti-government sentiment and government-led crackdowns. At least 23 people died there, the Local Coordination Committees of Syria said. The Syrian Observatory for Human Rights, another activist group, put the Homs death toll at 11 earlier in the day.
Demonstrations were taking place Saturday in several cities, including Idlib, Daraa, Deir Ezzor, and a suburb of the capital of Damascus, the LCC reported. At least four people were killed in Idlib and one in Hama, the LCC said.
The LCC said Friday that more than 3,800 people have died in Syria since anti-government protests erupted in March, amid the Arab Spring movements that have rocked the Middle East and North Africa. President Bashar al-Assad and other Syrian officials have blamed violence on outside forces attempting to undermine the 40-year rule of the president's family.
A resident of Homs, who asked that his name not be used to protect his security, said the heavy gunfire began Friday and continued with the military flying over Bab Amr, a nearby town. He said he could hear the activity from his home and was afraid to go into the street.
Massive explosions and intense shelling from tanks and artillery shells were also taking place in Homs, according to the LCC, an opposition group that organizes and documents protests.
The violence is the latest in a nearly eight-month uprising in Syria. It began with calls for elections and an end to abuses by security forces but turned into widespread and persistent calls for the ouster of al-Assad as the government's crackdown and demonstrations intensified.
The reports of violence came a day after a Homs doctor said 126 bodies had been taken to a hospital there in recent days. The doctor did not want to be identified out of fear of retribution by government forces.
The bodies, eight of which were burned, are unidentified. The doctor said their deaths have not been reported by the state-run news media.
The doctor's report was largely supported by LCC member Saleem Kabbani. Kabbani, who has provided CNN with reliable information in the past, cited three sources as having told him that approximately 100 unidentified bodies had been taken to the hospital in recent days.
Kabbani said his sources included a person who was involved in the transport of the bodies; a witness who saw the bodies in the location where they were found; and a witness inside the hospital.
He would not say where the bodies were found out of fear that doing so could lead to sectarian violence.
The government-run Syrian Arab News Agency said 22 slain people were taken from military hospitals for burial. The victims -- a civilian and personnel from the army and security forces -- were killed by "armed terrorist groups in Homs, Damascus countryside and Daraa while they were on duty," SANA said on Saturday.
Syria also announced the release of 553 detainees "with no blood on their hands," SANA said. The move coincides with Eid al-Adha, the celebration marking the climax of the Hajj, the annual Muslim pilgrimage.to Mecca.
CNN could not independently verify the accounts.
The Syrian government pledged Wednesday to the Arab League that it would pull back its forces, release prisoners and allow outside monitors into the country, but opposition activists said security forces fanned out in force after Friday prayers, surrounding mosques to prevent demonstrations and using gunfire to disperse crowds.
Arab League chief Nabil al-Araby met Saturday with member states to discuss future steps regarding the ongoing conflict.
Arab League ministers said the group would moderate a "national dialogue" after two weeks.
Syria has made previous pledges to withdraw armed forces from civilian areas, but in some of those cases, it withdrew only armored units and left infantry in place, or returned after a brief pullout. It also has made other moves aimed at defusing the protests, including plans to draft a new constitution, but they have failed to appease demonstrators.
CNN's Hamdi Alkhshali and Mohamed Fadel Fahmy contributed to this report.