Russia's Federal Security Service says it has arrested a group of Central Asian citizens suspecting of preparing an attack on public transport in a major Siberian city.

The security service, known by the acronym FSB, said the suspects arrested Friday in Krasnoyarsk had ties to "international terrorists."

The statement said agents had seized "the means of terrorist activity" from the suspects, who were not identified.

It is the second time this week the FSB has reported the arrests of Central Asians suspected of planning an attack. The first group was detained in Moscow.

The FSB said both attacks were planned for the May holidays, which culminate with Victory Day on Monday.

Concern is high in most former Soviet Central Asian states about the potential for the spread of Islamic extremism.