President Trump on Monday said that the planned terror attack in Russia thwarted by a CIA tip could have left thousands of people dead had the US not given its rival the heads up.

“I received a call from President Putin of Russia thanking our country for the intelligence that our CIA was able to provide them concerning a major terrorist attack planned in St. Petersburg where many people, perhaps in the thousands, could have been killed,” the president said during a speech on national security strategy in Washington, DC.

“They were able to apprehend these terrorists before the event with no loss of life and that’s a great thing, and the way it’s supposed to work. That is the way it’s supposed to work.”

In a series of raids last week, Russian authorities arrested members of a terror cell linked to ISIS in St. Petersburg, seized explosives, weapons and ammo and dismantled a bomb-making workshop, the state-run Russian media outlet RT reported.

The thugs had planned attacks on public places, including a suicide bombing and an explosion in the Kazan Cathedral in the city center.