JERUSALEM, Israel -- Syrian President Bashar al-Assad has been increasingly subject to international demands to end the deadly crackdown on anti-government protesters.
More than 2,000 protesters have been killed since the uprising began in mid-March.
Last week, the Arab League called for "an end to the spilling of blood" and appealed to Assad to "follow the way of reason before it is too late."
On Tuesday, Assad's security forces killed at least seven protesters, including a 13-year-old boy, at the start of the Eid al-Fitr festival that marks the end of Ramadan, The Associated Press reported.
The London-based Amnesty International said Tuesday that at least 88 people, including 10 children, have died behind bars in the five months since the protests began.
According to the human rights group, at least 52 of the corpses showed signs of torture, including whippings, beatings, electric shocks, and burns.
"The accounts of torture we have received are horrific. We believe the Syrian government to be systematically persecuting its own people on a massive scale," Amnesty's Neil Sammonds told Reuters.
Meanwhile, the U.S. Treasury froze the assets of Syrian Foreign Minister Walid Musallem, Syrian Ambassador to Lebanon Ali Abdul Karim Ali, and Assad advisor Bouthaina Shaaban.
State Department spokeswoman Victoria Nuland said the three have each played a role in "propagating and advancing the reign of terror that Assad is exacting on his own people."