US repeatedly warned Russia ahead of Moscow attack, White House says

National security spokesperson says US passed on warnings and dismissed Russian allegations Ukraine was involved as nonsense'

The US repeatedly alerted Russia that extremists were planning to attack large gatherings in Moscow ahead of last week's concert hall attack that claimed more than 140 lives, the White House has said.

The national security spokesperson, John Kirby, said on Thursday that US officials passed on warnings - including one in writing - and dismissed Russian allegations that Ukraine was involved as nonsense".