Syrian forces have tortured and killed civilians in the province of Homs in an assault that indicates crimes against humanity, and the Arab League should suspend Syria's membership, an international human rights group said Friday. The Arab League, which brokered a Syrian peace plan last week, scheduled an emergency meeting Saturday at its headquarters in Cairo to discuss the failure to stop the bloodshed. The UN estimates 3,500 have been killed nationwide since mid-March. Homs, Syria's third-largest city in a province of the same name, has emerged as the epicenter of the uprising. “Homs is a microcosm of the Syrian government's brutality,” said Sarah Leah Whitson, Middle East director at Human Rights Watch. “The Arab League needs to tell President (Bashar) Al-Assad that violating their agreement has consequences, and that it now supports Security Council action to end the carnage.” In a 63-page report released Friday, Human Rights Watch said security forces killed at least 587 civilians in Homs from mid-April to the end of August — the highest number for any single province. In the report, which focuses on that period, the rights group said former detainees reported torture including security forces' use of heated metal rods, electric shocks and stress positions. Witnesses also reported large-scale military operations during which security forces used heavy machine guns, including anti-aircraft guns mounted on armored vehicles. The group also acknowledged that some protesters and army defectors took up arms to protect themselves — a development that some fear plays directly into the regime's hands by giving it an excuse to use extreme violence against a mostly peaceful movement. “Violence by protesters or defectors deserves further investigation,” the report said.