The 2018 World Cup hosts Russia were grappling on Thursday with a new football hooliganism scandal after the unruly behaviour of fans who threw fireworks on the pitch forced the abandonment of a top-flight cup match. The referee called off fourth round Russia Cup match between Dinamo Moscow and their local rivals Torpedo Moscow in the 51st minute amid chaotic scenes with parts of the pitch blanketed in smoke and fireworks crackling on the turf. Police said that 20 fans were arrested as fights broke out between rival fan groups on the streets around the stadium before the match late Wednesday. The incident is a huge embarrassment for Russia days before it hosts a top FIFA delegation to announce the final list of the host cities for the 2018 World Cup.