(CNN) -- Syrian army defectors killed seven government security forces in an attack on a convoy Tuesday, a strike in response to the killings of 11 civilians, an activist group told CNN.
The Syrian Observatory for Human Rights said the incident took place in Idlib province in the northwest swath of the restive nation. It comes amid growing world outrage over the 9-month-long government crackdown on protesters in Syria.
The group said security forces had opened fire "indiscriminately" in the villages of Maarat Masreen and Kafr Bahmoul near the city of Idlib, killing 11 and wounding many others.
At least 36 people have died on Tuesday, said the Local Coordination Committees of Syria, another activist group. The 11 civilians were among 21 deaths in Idlib province; the group reported eight deaths in Hama, five in Homs and two in Daraa.
The affiliation of the defectors in this instance was not initially known, but one result of the stiff regime clampdown against the protesters has been the emergence of an armed opposition group of defectors -- the Free Syrian Army.
The Local Coordination Committees of Syria said tank shelling caused casualties in the village of Al-Jaah in Daraa province. The group attributes the shelling to the "big number" of Free Syrian Army troops there.
"The village is in dire condition, crimes against humanity are being committed and all basic services have been cut off along with any communication," the Local Coordination Committees of Syria said.
One activist told CNN two people died when a house was shelled in the western city of Homs.
CNN cannot independently confirm reports of violence in Syria because the government restricts the actions of foreign journalists.
More than 5,000 people have died in Syria, U.N. Commissioner for Human Rights Navi Pillay said Monday, a figure rejected by Syrian ambassador to the United Nations as "incredible."
But Pillay, who briefed the U.N. Security Council and spoke to reporters afterward, called the situation "intolerable" and said she is "appalled by the constant stream of grave violations that have taken place since the first protests in Syria in March." She said "the nature and scale of abuses" indicate that Syrian forces likely committed "crimes against humanity."
These deaths include civilians, defectors and those executed for refusing to shoot civilians. It doesn't include security and military forces, but the United Nations said hundreds of them "are also thought to have been killed."
The Syrian government, meanwhile, has consistently blamed the violence on "armed terrorist" gang members and denied any efforts to target peaceful civilians.
While Syria is becoming more isolated, Russia -- a longtime friend of the Mideastern country -- has not joined in the worldwide chorus of condemnation against the regime. Russia believes "the Western and Turkish pressure on Syria is an encroachment on its traditional spheres of influence," a Foreign Affairs article said. It was one of four countries that voted against a U.N. Human Rights Council resolution this month condemning widespread violations of human rights in Syria.
Russian Foreign Minister Sergey Lavrov on Tuesday accused the Syrian opposition of trying to provoke a humanitarian crisis to justify foreign military intervention.
"It seems to me that, beyond any doubt, the goal is to provoke a humanitarian catastrophe and get an excuse to demand foreign intervention in this conflict," Lavrov said at a news conference, arguing that Syria should accept Arab League proposals for ending the violence and allow foreign observers in the country.
The United States, European Union, Turkey and the Arab League have imposed sanctions. But Lavrov also said that "history shows that sanctions never work, with very rare exceptions, and we are not ready to use them except as a last resort."
Tony Badran, who wrote the Foreign Affairs article, said Syria gives "Russia a foothold in the Mediterranean through a shared naval maintenance facility at the Syrian port city of Tartus."
"It should have been no surprise that after the Arab League moved against (President Bashar al-Assad), Moscow announced that it would continue to honor all arms contracts with the Syrian government and would be sending warships to make port calls in Syria this summer," he wrote.
Meanwhile, opposition figures said the Syrian government had warned people in Homs to stop anti-government protests, hand in their weapons and surrender defecting military members by Monday night -- or face attack by government forces.
Syrian forces gave a 72-hour warning, said Lt. Col. Mohamed Hamdo of the Free Syrian Army, the opposition group of defected Syrian military personnel. Activists on the ground said the ultimatum was issued Friday for Homs. The government has not acknowledged any deadline for Homs in state-run media, and it was not clear Tuesday morning what had happened in the city overnight.