The White House on Sunday confirmed media reports from Russia that US President Donald Trump had spoken to Russia's Vladimir Putin on Sunday.

It followed reports by Russia's state news agency TASS that Putin had called Trump to thank him and the Central Intelligence Agency (CIA) for providing information that helped thwart a planned attack by "Islamic State" (IS) assailants on St. Petersburg.

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"The Russian president thanked his American colleague for the information passed on by the Central Intelligence Agency, which helped detain a group of terrorists preparing explosions in St. Petersburg's Kazansky Cathedral and other busy sites in the city," the Kremlin said in a statement.

According to Russian media, Putin also reassured Trump that Russia's intelligence service would transmit any information pertaining to the attacks on the US to the White House, as it had done in the past.

In a readout of Sunday's call, the White House said that Trump had told Putin "that he and the entire United States intelligence community were pleased to have helped save so many lives."

Sunday's call was the second time Trump and Putin had spoken in just three days. On Thursday, the White House said Trump and the Russian president had discussed ways to work together in addressing North Korea's nuclear weapons program.

Relations between Russia and the US remain tense. While Trump and Putin are believed to get along well, the FBI and an intelligence committee set up by the House of Representatives continue to investigate allegations of collusion between the Trump campaign team and Kremlin officials in the run-up to last year's US presidential election.

Russia on high alert going into 2018

On Friday, Russia's FSB security service said it had arrested seven members of an Islamist terror group planning "the killing of citizens" in a series of suicide attacks in Russia's second city on December 16.

Among the targets was the city's famous Kazansky Cathedral, a popular tourist site.

Police raided a St. Petersburg apartment where they uncovered a "large number of explosives used to make homemade bombs, automatic rifles, munitions and extremist literature," the FSB said in a statement.

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The arrests followed warnings raised by FSB chief Alexander Bortnikov, who said Russia was on high alert for the return of jihadis from Syria. Next year will be a crucial one for Russia, with the country having its presidential election in March, before hosting the FIFA World Cup in the summer.

Friday's arrests were also reminiscent of last April's terrorist attack in St. Petersburg, in which 15 people were killed in an explosion on a metro train. The assailant was identified as a 22-year old Kyrgyz-born man, although no group has claimed responsibility for the incident.

dm/tj (AP, Reuters, AFP, dpa)