Syrian rebels executed at least a half-dozen unarmed government soldiers Thursday after attacks on checkpoints near the town of Saraqeb in northwest Syria.

At least 28 soldiers and five opposition fighters were killed in the rebel operation, which targeted checkpoints on roads connecting Saraqeb to Aleppo and Ariha, according to the Britain-based Syrian Observatory for Human Rights.

The execution of the soldiers, which was documented in a graphic video posted online Thursday, is not the first time that rebel fighters appear to have committed war crimes. U.N. representatives and human rights organizations have repeatedly criticized the Syrian opposition in recent months for carrying out summary executions and for abusing detainees.

In early August, members of a clan loyal to Syrian President Bashar al-Assad were executed by rebels, and a video of the killings was widely disseminated on the Internet. The executions prompted some commanders of the opposition Free Syrian Army to draft a code of conduct for their fighters in an attempt to curb human rights abuses. But the execution of the soldiers Thursday indicated that the code is not being observed by all rank-and-file rebel fighters.

The Syrian government also has been heavily criticized for human rights abuses by the military and shabiha militiamen.

A look at the Syrian uprising nearly two years later. Thousands of Syrians have died and President Bashar al-Assad remains in power, despite numerous calls by the international community for him to step down.

Meanwhile, heavy fighting broke out in Damascus on Thursday, and government jets bombed the Jobar neighborhood in the city, according to opposition groups.

The Observatory said that at least 120 people were killed in fighting across the country Thursday.

Fighting continued unabated through the four-day Eid al-Adha holiday, which ended Monday, despite a push by U.N. envoy Lakhdar Brahimi to secure a truce.

Brahimi visited Beijing on Wednesday, where Chinese Foreign Minister Yang Jiechi proposed a cease-fire followed by a gradual transition of power. China is a close ally of the Syrian government, as are Russia and Iran.

Brahimi traveled to Cairo on Thursday and was expected to meet the head of the Arab League, Nabil Elaraby, to discuss the Syrian conflict.

The video posted online Thursday was allegedly filmed at the Hamisho checkpoint west of Saraqeb. It shows rebel fighters kicking and insulting the government soldiers, who are spread out on the ground. Some of them appear to be wounded. One of the soldiers pleads, “I did not hit anyone, by Allah. I did not kill anyone.”

The man filming the video tells the soldier to shut up and directs his comrades, “Organize them for me.” The fighters pull the soldiers to the center of the room and open fire on the group, kicking up clouds of dust. The shooting continues for 20 seconds.

A second video posted online Thursday, which appears to have been filmed shortly after the execution, shows at least three other bodies spread out around the checkpoint. The man filming approaches two of the bodies and says, “The shabiha of Assad, the dogs.”

Ahmed Ramadan contributed to this report.