The Russian counterintelligence agency has announced the arrest of two suspected supporters of the Islamic State group who it says were planning a terror attack.

The FSB said Wednesday the two men were arrested in an apartment in Yuzhno-Sakhalinsk, a city on the Pacific island of Sakhalin.

It said one was a citizen of Russia and the other of one of the former Soviet republics in Central Asia. They were not identified.

The agency said a search of where they were living turned up a homemade explosive device and IS propaganda literature.

The FSB has appeared eager to demonstrate its ability to prevent attacks following this month's suicide bombing on the St. Petersburg subway that killed 14 passengers. The bomber was from Kyrgyzstan.