SYDNEY - Britain and Russia have both topped their Groups and made it through to the quarterfinal stage of the ATP Cup on Tuesday evening, joining Serbia and host Australia in the final eight of the inaugural tennis tournament held in Sydney, Perth and Brisbane.

On day five action in Western Australia, Russia eclipsed Norway 3-0 without dropping a set, while Italy also thrashed the US 3-0 thanks to the help of world number 12 Fabio Fognini, who was victorious in both his singles and doubles match-ups.

In other contests of the 24-nation round robin tournament, Britain blasted Moldova off the court 3-0 in Sydney, while Belgium snuck past Bulgaria 2-1 after world number 11 David Goffin edged out powerhouse Grigor Dimitrov 4-6, 6-2, 6-2.

In Brisbane's day session, Canada overcame Germany 2-1 as world number seven Alexander Zverev's horror run of form continued against Denis Shapovalov, going down in the battle 6-2, 6-2 after making a number of double faults and unforced errors.

As the evening matches rolled around local fans were treated to a mouth-watering showdown between two of the sport's most dynamic young players when Aussie Nick Kyrgios took on Greek world number six Stefanos Tsitsipas.

During the gripping encounter, a frustrated Tsitsipas smashed his racket along the seating area.

In the end it was Kyrgios who eventually snatched the close-fought match 7-6(7), 6-7(3), 7-6(5), leading the Aussies to a 3-0 victory over Greece.

When asked about the strange incident post match, Tsitsipas told reporters "It happened accidentally".

"I didn't mean to do it and straight away forgot about it and moved on from there," he said.

"I wasn't aiming to do that, so it went out of control, unfortunately."

With Australia, Serbia, Britain and Russia all confirming their sports in the quarterfinals, the remaining places will be decided on Wednesday as day six action continues.