A CIA tip-off to their Russian counterparts foiled a plot to bomb St Petersburg’s Kazan Cathedral and other crowded sites at the weekend, the Kremlin said.
The counter-terrorist cooperation came even as Russia-U.S. ties have plunged to their lowest level since the Cold War era — first over Russia's annexation of Crimea and support for pro-Russia separatists in Ukraine, more recently over allegations that Moscow interfered in the U.S. presidential election to help Trump.
While Russian officials have said the two countries were continuing to exchange some terror-related intelligence, Sunday's statement from the Kremlin was Russia's first public assertion that information from the United States helped prevent an attack.
"The information received from the CIA proved sufficient to find and detain the criminal suspects," the Kremlin said.
Russian President Vladimir Putin telephoned US President Donald Trump on to thank him for the CIA tip, the Kremlin and the White House said.
"President Trump appreciated the call and told President Putin that he and the entire United States intelligence community were pleased to have helped save so many lives," the White House said in a statement.
The Federal Security Service, or FSB, said on Friday that seven suspected followers of ISIL had been arrested for allegedly planning to carry out terror attacks in St. Petersburg this weekend.
The agency said the suspects were plotting a suicide bombing in a church and a series of other explosions in the city's busiest areas this coming weekend on ISIL orders.
It said a search of a St. Petersburg apartment found explosives, automatic weapons and extremist literature. Russian news reports said that Kazan Cathedral, a landmark 19th century Russian Orthodox church on St. Petersburg's central Nevsky Prospect, was the prime target.
If the suspects succeeded in bombing the cathedral, it would have been the first major attack on a Russian Orthodox Church by Islamic terrorists, who have blown up apartment buildings, passenger planes and transport facilities in Russia.
In April, a suicide bombing in the St. Petersburg's subway left 16 dead and wounded more than 50.
Russian TV stations have aired footage daily since Friday of the suspects in the foiled attacks being apprehended and questioned.
One segment showed FSB operatives outside a St. Petersburg apartment building detaining a suspect, who appeared later saying he was told to prepare homemade bombs rigged with shrapnel.
"My job was to make explosives, put it in bottles and attach pieces of shrapnel," the suspect, identified by Russian media as 18-year old Yevgeny Yefimov, said in the footage released by the FSB.
Last week, the FSB said it also arrested several ISIL-linked suspects in Moscow, where they allegedly were plotting a series of suicide bombings to coincide with New Year's celebrations.