Is This Keystone Cops Story True?

Eric Margolis of the Toronto Sun writes (emphasis added):

During 1999, Moscow and a provincial city were racked by a series of apartment building bombings that killed 300 people. Panic swept Russia.

The bombings were blamed on "Chechen Islamic terrorists." But Moscow police caught a team of SVR [Russian intelligence agency for foreign affairs] agents red-handed planting explosives in a residential building. The agents claimed they were running a "security test."

Question: Is this story true?