The Syrian government is committing “crimes against humanity”, says a human rights group, urging the Arab League to suspend the country's membership.
Human Rights Watch published the report on Friday, detailing the on-going violence within the Syrian state.
Fifteen people were reportedly killed on Thursday, victims of the regime’s brutal crackdown.
According to the United Nations (UN), more than 3,500 Syrians have perished since the uprising began.
Compounding the reports, a video has emerged showing soldiers and rebel fighters locked in a firefight. It is believed the video, published by Al Jazeera, was filmed in the city of Homs.
According to Sarah Leah Whitson, Middle East director at Human Rights Watch, "Homs is a microcosm of the Syrian government's brutality."
"The Arab League needs to tell President Assad that violating their agreement has consequences, and that it now supports Security Council action to end the carnage," she told the Associated Press.
With the death toll mounting, the Arab League is coming under increasing pressure to suspend Syria’s membership, while Human Rights Watch has urged the UN to ramp up sanctions against the embattled state.
Based on the accounts of more than 100 victims of the Syrian security forces, the 63-page report highlights the use of torture, including the use of heated metal rods and electric shocks, and claims that Syrian security forces have killed at least 587 civilians in Homs between April and August, with more than 100 killed in the last week.
The document also accused government forces of the systematic use of “lethal force against demonstrators”.
"Violence by protesters or defectors deserves further investigation," the report said. "However, these incidents by no means justify the disproportionate and systematic use of lethal force against demonstrators, which clearly exceeded any justifiable response to any threat presented by overwhelmingly unarmed crowds."
On Wednesday, UN human rights chief Navi Pillay raised the prospect of all-out civil war in Syria, with the government’s increasingly brutal treatment of the protesters causing members of the Syrian army to defect.
Many of the defectors are joining the Free Syria Army. The outfit, based in Turkey (with Turkish consent), has repeatedly clashed with forces loyal to the regime.
The Free Syria Army claims to be 15,000-strong, though reports suggest the figure is exaggerated.
On Friday, the Syrian Observatory for Human Rights reported protests in the Damascus suburbs, Daraa in the south and Idlib near the Turkish border, with the increasing bloodshed raising the prospect of President Assad seeking refuge in one of Syria's neighbouring Arab states.
According to US assistant secretary of state Jeffrey Feltman, several states have expressed a willingness to harbour the president should he seek exile.
Speaking before a Senate committee, Feltman said: “Almost all the Arab leaders and foreign ministers whom I talk to say the same thing: Assad's rule is coming to an end. It is inevitable. Some of these Arabs have even begun to offer Assad safe haven to encourage him to leave.”
Feltman did not indicate which states are willing to take Assad, though Saudi Arabia is a possible destination should he choose to leave.