Amnesty International says Syrian security forces may have committed crimes against humanity during a deadly operation last month in a town near the Lebanese border.

The London-based rights group issued a report Wednesday accusing Syria of rounding up scores of male residents in Talkalakh and torturing most of them. It quotes witnesses that say at least nine people died in custody.

The Amnesty report says the assault appears to be part of a “widespread, systematic attack against the civilian population” that constitute crimes against humanity. It urged the U.N. Security Council to refer the situation in Syria to the International Criminal Court.

On Tuesday, Syrian government forces opened fire on civilians in the central city of Hama, killing at least 11 people. Activists said the shootings took place after troops moved tanks around the city's outskirts in apparent preparation for an assault.

In response, residents set up dozens of roadblocks and set debris on fire to prevent the advance of tanks circling the town. Hama residents burned tires and trash bins and set up sand barriers and other obstacles to block the expected assault.

Security forces also mounted a second attack Tuesday in northwest Idlib province.

The U.S. and Britain urged Syria to immediately pull its forces from Hama and other cities.

Hama is one of the centers of opposition to President Bashar al-Assad's 11-year autocratic rule, and was the site of an anti-Assad rally on Friday that drew hundreds of thousands of protesters.

On Monday, soldiers sealed off the city and raided homes there, one month after government forces withdrew. At least 20 people were arrested as part of Syria's ongoing crackdown on dissent.

Unlike its European partners and the U.S., France says Mr. Assad has lost his legitimacy to rule. But a French campaign for U.N. condemnation of the crackdown has met stiff Russian and Chinese resistance.

Foreign Minister Alain Juppe said Tuesday there are signs that Russia is beginning to question its policy on Syria. Juppe said he attempted to sway his Russian counterpart, Sergei Lavrov, but that Russia is still threatening to veto any U.N. resolution against Syria.

Rights groups say Syrian security forces have killed at least 1,400 civilians since mid-March while trying to suppress the anti-government uprising. The Syrian government says terrorists and Islamist militants have killed hundreds of security personnel during the same period.