Reporting from Beirut— Syria’sarmed rebels have committed “”serious human rights abuses,”” including kidnappings and torture, and reportedly executions, of security personnel and civilians, Human Rights Watch said Tuesday. The group painted a dark picture that is in stark contrast to the “”freedom fighter”” image that the rebels and their political allies outside Syria have sought to project to the world. In an open letter to the opposition, Human Rights Watch depicts a decentralized, disparate guerrilla structure in which armed groups seem to operate with complete autonomy, sometimes acting on sectarian motives to kidnap and kill security force members and civilians considered pro-government. The allegations come as the United States and other nations that have voiced support for the Syrian opposition contemplate additional actions to support the resistance, including the possibility of arming the rebels seeking to topple the government of President Bashar Assad. But U.S. and other officials have also expressed reservations about the possibility that Islamic militants, including Al Qaeda, may be part of Syria’s insurgency. In Syria, rebels Tuesday reportedly suffered yet another setback, announcing a withdrawal from the eastern city of Dair Alzour, a frequent site of antigovernment protests. A government offensive in recent weeks has driven insurgents from several other strongholds, including the city of Idlib in the northwest and parts of the central city of Homs. But Syrian rebels have proved capable of regrouping once Syrian forces and their tanks depart. At the United Nations, diplomats were working on a resolution supporting the Syrian peace mission of former Secretary-General Kofi Annan, a special envoy of the world body and the Arab League. Moscow, which vetoed a previous Security Council resolution that would have called on Assad to cede power, in recent days has publicly accused the Syrian president of making errors and not moving quickly enough toward reforms. But there is no indication that Moscow will abandon Assad, its longtime ally. Human Rights Watch’s report critical of the insurgents follows cases in which the group has documented widespread violations by Syrian security forces, including disappearances, torture, arbitrary detentions and indiscriminate shelling of neighborhoods. In its latest report, the group includes statements from witnesses suggesting that some insurgent atrocities may stem from animosity against minority sects, notably Shiite Muslims and members of the offshoot Alawite sect. Assad and many high-ranking members of the security services are Alawites. One Syrian activist, identified only as Mazen, told Human Rights Watch that members of one armed faction known as the Abu Issa group had kidnapped pro-government residents in northern Idlib province and tortured three of them to death. In another incident in the strife-torn Idlib region, a witness identified as Samih described a kidnapping-for-ransom scheme run by another group, the Al Nur battalion. The witness identified the group as Salafi, a conservative Sunni Muslim movement that has in some cases been associated with militancy. In one especially grisly episode, an Alawite resident of Homs told the rights group that armed gang members entered his neighborhood on Jan. 23 and took his elderly parents from the family home. The gang leader first demanded money, but the man’s parents later were found dead, their bodies displayed in a YouTube video, the report says. “”This is a sectarian crime,”” the son, identified only as Marwan, told Human Rights Watch. “”My father has nothing to do with the government.”” Human Rights Watch said it had reviewed at least 25 videos on YouTube in which Syrian security forces or their alleged supporters confess to crimes “”under duress.”” In at least 18 cases, “”these videos show detainees who are bruised, bleeding or show other signs of physical abuse.”” Human Rights Watch called on Syrian opposition groups to condemn atrocities by antigovernment forces. There was no immediate reaction from the Syrian National Council, the best-known Syrian opposition coalition, which is based in Istanbul, Turkey. More than 8,000 civilians and antigovernment combatants have been killed during the yearlong uprising, according to the United Nations. The Syrian government says more than 2,000 security personnel have lost their lives.