Finance minister Jeremy Hunt on Sunday said that the UK had "very little confidence" in Russia's statements on the Moscow concert hall attack, accusing it of trying to "defend" it's assault on Ukraine.

At least 133 people were killed by armed gunmen at the Crocus City Hall in a suburb on the northern edge of Moscow on Friday, with the Islamic State group claiming responsibility for the attack.

Russian authorities have not yet blamed the group, but president Vladimir Putin has said the attackers were apprehended while "travelling towards Ukraine where, according to preliminary information, they had a window to cross the border".

Russia's FSB security service said earlier that the assailants had been "in contact" with people in Ukraine as they tried to flee the country.

Britain's Chancellor of the Exchequer Hunt told Sky News on Sunday that "I take what the Russian government says with an enormous pinch of salt... after what we've seen from them over the last few years.

"We know that they are creating a smokescreen of propaganda to defend an utterly evil invasion of Ukraine.

"But that doesn't mean that it's not a tragedy when innocent people lose their lives, when you have horrible bombings," he added.

The minister warned that the UK and other European countries should "absolutely" be concerned about the re-emergence of IS on the world stage.

"We are very lucky in this country that we have incredibly impressive intelligence agencies who have been successful... in foiling a lot of terrorist threats over recent years, but we have to remain vigilant," he told Sky News.

"If it is Islamic State, they're utterly indiscriminate in what they do, they're prepared to murder in the most horrific way."