(CNN) -- At least 16 people were killed by security forces across Syria Saturday as unrest there continued, a human rights organizations said.





Three people were killed in the city of Homs, where a strong military presence was reported, the London-based Syrian Observatory for Human Rights said. Another three were killed in Hama province.





The Local Coordination Committee of Syria reported that Syrian security forces were storming the Damascus suburb of Zabadany and were shelling housing and positioning snipers. The group also announced, in a separate incident, the killing of Dr. Ibrahim Nahel Othman, who they described as "one of the most important physicians in the Syrian Revolution." He was killed by gunfire near the Turkish border, the group said.





Another group, the Coalition of Free Damascus for Peaceful Change, said that the doctor was a wanted man because he performed many surgeries on wounded protesters.





The reported deaths came amid tensions in Homs -- a center of regime arrests -- as military troops manned more than 60 checkpoints inside the city and surrounded it, according to the Syrian National Council, a leading opposition movement.





A feared full-scale crackdown did not happen Saturday, but activists posted a video Saturday that they said showed the military harassing residents of Homs.





Mourners on Friday went to bury a 10-year-old boy, Maher al-Husseini, who was allegedly killed by a sniper's bullet in his own home.





The video shows the boy wrapped in a white sheet and carried by men in street towards a cemetery. Some of the men chant "The martyrs blood will not be lost in vain," as the lifeless boy is carried.





As the men walk towards the cemetery, gunfire can be heard. They get to the cemetery and start digging as gunfire continues to ring out.





CNN could not independently confirm what was depicted in the videos. Western networks are not allowed inside the embattled country.





The United Nations said last week that more than 4,000 people have died in Syria since a government crackdown against protesters erupted in mid-March. The regime's actions have outraged world powers and sparked sanctions by the Arab League, Turkey, the United States and the European Union.





The council said the Bashar al-Assad regime is "driving violent sectarian incidents to justify this potential murder." More than 30 corpses -- all thought to be victims of sectarian violence -- were found Monday in Homs.





The city of Homs is in a province of the same name.
How much people died in Syria? Where the video comes from? What is the opposition?
4,000 activists Syrian National Council,
question: How much people died in Syria?, answer: 4,000 | question: Where the video comes from?, answer: activists | question: What is the opposition?, answer: Syrian National Council,