The Kremlin and the White House say that U.S. intelligence services helped Russia thwart a series of terrorist attacks in St. Petersburg by tipping off Moscow about the purported plot.
In an unusual public airing of details about counterterrorism cooperation, the Kremlin said Russian President Vladimir Putin thanked U.S. President Donald Trump in a phone call earlier on December 17 for information that the U.S. Central Intelligence Agency (CIA) provided on the alleged planned attacks.
The call, which the White House said was initiated by Putin, was the second between the two leaders in a four-day span and came two days after Russian authorities said they had detained seven suspected Islamic extremists accused of planning bombings in Russia's second city.
The Kremlin said in a statement that the information from the CIA helped track down and "detain terrorists" and that Putin "assured" Trump that Russian security services would relay to their U.S. counterparts any information about terrorist threats to the United States and its citizens.
The Kremlin added that Putin had asked Trump to pass along his thanks to CIA Director Mike Pompeo, which the White House said the U.S. president had done.
"No Russian lives were lost and the terrorist attackers were caught and are now incarcerated," the White House said in a statement.
"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."
Trump has repeatedly said he wants to improve relations with Moscow and that counterterrorism efforts in Syria and elsewhere could serve as a cornerstone of better ties.
But relations between Moscow and Washington continue to be mired in tension over what U.S. intelligence agencies say was a Russian campaign to meddle in the 2016 U.S. presidential election, Russian interference in Ukraine, and mutual accusations of violating arms-control agreements.
Multiple U.S. investigations are under way into the alleged election meddling and whether associates of Trump colluded with Moscow. Putin denies that Russia interfered, and Trump says there was no collusion.
The White House readout said that Trump stressed to Putin in the call "the importance of intelligence cooperation to defeat terrorists wherever they may be."
"Both leaders agreed that this serves as an example of the positive things that can occur when our countries work together," the White House said.
In a December 14 news conference in Moscow, Putin offered a positive assessment of Trump's presidency, citing growing markets, and said that he hoped U.S-Russian ties will recover.
But he also repeated Moscow's denial that it interfered in last year's U.S. presidential election and its accusation that Washington had violated the 1987 Intermediate-Range Nuclear Forces (INF) treaty.
Washington alleges that Russia has developed a missile that violates the treaty.
In a December 14 telephone call following Putin's press conference, Trump thanked the Russian president for his comments "acknowledging America's strong economic performance," a White House readout said, adding that they also discussed North Korea's nuclear program and ballistic missiles.
Earlier on December 17, Trump's ambassador to Russia said on Twitter, "I think we will expect to see further improvements in the U.S.-Russia relationship."
"The American people expect it and demand it, and the Russian people expect it and demand it as well," U.S. Ambassador Jon Huntsman added in the tweet posted by the U.S. Embassy in Moscow.
The detentions of the seven suspects in the alleged planned bombings in St. Petersburg was announced by Russia's Federal Security Service (FSB) on December 15.
The agency said they were suspected members of the extremist Islamic State group and that they were being directed from abroad via the messaging app Telegram. It said a raid on an apartment in St. Petersburg had uncovered a cache of weapons, explosives, and extremist materials.
The FSB released footage that has been aired on Russian television in which one of the suspects, identified in the Russian media as Yevgeny Yefimov, says he was tasked with preparing homemade explosives packed with shrapnel.
A St. Petersburg court on December 17 ordered three of the suspects to remain in custody until January 14, Russia's state-run RIA Novosti news agency reported.
Two of the men are from Russia's southern North Caucasus region, while the third is from the ex-Soviet republic of Tajikistan in Central Asia.
The press service for St. Petersburg's court system said the three men deny the allegations and claim that "weapons were planted on them."
Yefimov and a fifth suspect -- Anton Kobyets -- were previously ordered to remain in custody by a St. Petersburg court.
The status of the other two suspects cited in the FSB statement was not immediately clear.
With reporting by AP, Reuters, TASS, RIA Novosti, and Interfax