Police work on the site of a knife attack in the center of Surgut, Russia, on Aug. 19, 2017. (Xinhua/Sputnik)

MOSCOW, Aug. 31 (Xinhua) -- The Russian Federal Security Service (FSB) said Thursday it has detained two individuals from Central Asia suspected of planning terrorist attacks.

It said in a statement that one of the detainees posted on the Internet a video message to the Islamic State (IS) pledging allegiance and declaring a plan to attack people with a knife.

The second detainee admitted that he was an IS member and was going to become a suicide bomber, the FSB said, adding that an improvised explosive device was found at his residence.

They planned to carry out terrorist attacks in Moscow and the surrounding region on Friday when the academic year starts in Russia.