CAIRO — An international human rights group said Friday that visits to two Syrian security centers recently captured by rebel fighters contained proof of widespread, arbitrary detentions and torture by the government of President Bashar al-Assad.

The group, Human Rights Watch, said the centers provided a rare glimpse into the extensive security and intelligence apparatus that the Assad government has mobilized to try to quash the uprising against his rule.

Among its findings were the use of solitary confinement cells and a cross-shaped device known as the “the flying carpet” to which detainees were tied so they could be beaten and bent into painful, sometimes harmful positions. The group also found lists of university graduates.

Rights groups have long accused the Syrian government’s many security and intelligence agencies of intimidating and silencing foes by detaining them without charge in centers where torture is routine. Many detainees disappear.