Syrian Insurgents Accused of Rights Abuses Giorgos Moutafis/Agence France-Presse - Getty Images Defectors with the Free Syrian Army resting in Idlib Province on Saturday. The continued violence suggests that diplomacy has made little headway. BEIRUT, Lebanon - Armed Syrian defectors took their uprising into the heart of a heavily guarded and wealthy district of Damascus on Monday, clashing with security forces in what activists and residents called the most intense fighting in such a strategic area since the protests against President Bashar al-Assad began a year ago. But a human rights group offered a more complex vision of the insurgents on Tuesday, accusing them of a catalog of abuses including "kidnapping, detention, and torture of security force members, government supporters, and people identified as members of pro-government militias, called shabiha." The flaring of violence in the Syrian capital followed a weekend in which bombers struck at government targets in both Damascus and Aleppo, Syria's largest cities, raising concerns that the scope of the armed uprising was expanding into places that had been largely spared from violence. The clashes in Damascus also coincided with the arrival of a monitoring team sent by Kofi Annan, the special representative on Syria for the United Nations and the Arab League. Mr. Annan is trying to advance his effort to start a dialogue between the antagonists in the Syria conflict and open the way for humanitarian aid. There were also signs that Russia, Mr. Assad's most important foreign supporter, was exerting some pressure on him to allow a daily pause in the fighting and to permit outside aid to victims of the conflict, which the United Nations has estimated has left more than 8,000 dead and thousands more displaced. But the timing, location and intensity of the Damascus clashes suggested that diplomacy had made little headway in resolving the conflict. By contrast, the Syrian Army appeared to have advanced significantly in recent days against rebel enclaves around the country, from the northern city of Idlib to Dara'a in the south, the birthplace of the protests that began last March. As the year-long uprising has grown ever bloodier, international human rights investigators have assailed the Syrian authorities for the bulk of abuses, saying those by armed opponents of Mr. Assad are on a lesser scale. But, accusing the opposition of abuses, an open letter to the Free Syrian Army insurgents from the New York-based Human Rights Watch said Tuesday that some armed attacks by opposition groups were motivated by religious and sectarian sentiments arising from the association of some communities with government policies. "The Syrian government's brutal tactics cannot justify abuses by armed opposition groups," said Sarah Leah Whitson, Middle East director at Human Rights Watch. Opposition leaders should make it clear to their followers that they must not torture, kidnap, or execute under any circumstances. Human Rights Watch also repeated that it had documented "widespread" violations by Syrian government forces "including disappearances, rampant use of torture, arbitrary detentions, and indiscriminate shelling of neighborhoods." The letter said antigovernment groups reported to be carrying out abuses "do not appear to belong to an organized command structure or to be following" the orders of the opposition's exiled political leaders in the Syrian National Council. In Monday's fighting in Damascus, the Syrian Observatory for Human Rights, an opposition group based in London, said its informers had reported that at least 18 members of the security forces were killed. The official SANA news agency put the toll much lower, saying one member of the security forces and two opposition fighters were killed in a raid on a "hide-out of an armed terrorist group" in the affluent district. It was impossible to independently corroborate the differing accounts because of government restrictions on outside reporting in Syria. But residents and activists reached by telephone and Skype said it was extraordinary to see such clashes in a well-defended area of Damascus so close to crucial security installations and the homes of powerful figures. We stayed awake and couldn't sleep till around 5 a.m. The fighting started around 2 a.m. or 3 a.m. with several explosions, activists and residents said, followed by automatic-weapons fire and helicopters circling with searchlights, in a wealthy area of the Mezze district that is home to businesspeople, United Nations offices and diplomatic residences. Smoke was seen rising near an upscale supermarket and the high-rise Tala Tower, decorated with a seven-story image of a smiling Mr. Assad. One resident reached by telephone said he had heard three explosions and seen exchanges of gunfire between two buildings near the tower, a residential building and another where security forces had been positioned. The resident, who gave his name only as Moaz, said that the battle lasted three hours and that government forces evacuated the residential building and cut the power before mounting a raid. "We had a terrible night," said another nearby resident who was reached by telephone. The woman, in her mid-30s, said she was too afraid to send her daughter to school. Reporting was contributed by Alan Cowell from London; Hala Droubi from Jidda, Saudi Arabia; Hwaida Saad from Beirut; Ellen Barry from Moscow; and J. David Goodman and Rick Gladstone from New York.