Russia said it had thwarted terror attacks reportedly planned in St Petersburg as the result of a tip from Washington, as President Vladimir Putin personally thanked his US counterpart Donald Trump.

Russian news agencies cited the Federal Security Service (FSB) as saying that as a result of the information, two Russians had been detained on 27 December on suspicion of plotting attacks during new year festivities in St Petersburg.

The Kremlin said Putin passed on his gratitude to Trump for the tip from US special services during a phone call on Sunday. It gave no further details.

Diplomatic ties between Washington and Moscow are fraught over disagreements concerning Ukraine and Syria and allegations of Russian meddling in the US presidential election, but Trump and Putin have kept personal lines of communication open.

Two years ago, the Russian leader phoned Trump to thank him for a tip that Russia said had helped prevent a bomb attack on a cathedral in St Petersburg. Russia has repeatedly been the target of attacks by militant groups including Isis.

The Kremlin said in a statement that Putin and Trump had agreed to continue bilateral cooperation to tackle terrorism.