Amnesty says at least 13,000 people hanged at Syrian prison

Amnesty International says Syrian authorities killed at least 13,000 people in mass hangings at a prison north of Damascus known to detainees as the "slaughterhouse."

The group released a report Tuesday covering the period from the start of the 2011 uprising until 2015, during which Amnesty says groups of 20 to 50 people were hanged at Saydnaya Prison, once or twice a week. It says the killings were authorized by senior officials, including deputies of President Bashar Assad.

Amnesty says it interviewed 31 former detainees and more than 50 officials, including prison guards and judges.

Syrian officials rarely comment on widespread allegations of torture in the country's notorious prisons. They have denied accusations of mass killings.