As the first round of group games at the 2018 World Cup is completed today, we look back at some of the most notable incidents involving the use - or non-use - of the new Video Assistant Referee system so far.

VAR  is available to help guide match officials at the tournament on incidents in the build-up to goals or penalties, as well as straight red cards or cases of mistaken identity.

It will only be used to "correct clear and obvious errors and missed incidents in clearly defined match-changing decisions", according to FIFA.

Your guide to VAR

June 18 - Tunisia v England


England defender Kyle Walker was astonished to see a penalty awarded against him when Fakhreddine Ben Youssef went to ground after being caught by his arm as he attempted to prevent the frontman from reaching a 33rd-minute cross. Ferjani Sassi converted the resulting spot-kick to level the scores at 1-1.

Walker said afterwards that players were still confused about the apparently haphazard use of the system.

"We've had a briefing, but what's correct and what's not?" he said. "When do you ask for it? You don't want to crowd the referee and say 'VAR' because then it is a yellow card.

"I think you just have to let the referees get on with it and let them take the decisions. They have got a hard enough game as it is without putting any more confusion in it.

"It is one of those things that I am going to have to take on the chin. Would it have been given in the Premier League? Probably not. In the World Cup it is probably a penalty."

June 18 - Tunisia v England
Sassi found himself in the thick of the action once again seven minutes later when he appeared to wrestle Kane to the ground inside the penalty area. The England captain protested immediately, but Roldan was unmoved and was not invited to take another look at the incident.

June 18 - Tunisia v England
Kane appeared to be hauled down for a second time six minutes after the restart with defender Yassine Meriah this time the alleged offender. But again, the officials allowed play to continue with no word to the contrary from VAR referee Sandro Ricci and his team.

June 18 - Sweden v South Korea
Sweden's winning penalty was awarded following review by VAR. Referee Joel Aguilar initially allowed play to go on after Viktor Claesson was hacked down by Lee Jae-sung, but called a halt moments later after a word in his ear.

He looked at the incident again on the pitch-side screen before pointing to the spot and Andreas Granqvist duly obliged.

June 17 - Brazil v Switzerland

Brazil players complained long and hard that defender Miranda was pushed by Steven Zuber when he headed home Switzerland's equaliser early in the second half of their Group E opener on Sunday.

They also believe Gabriel Jesus was manhandled inside the penalty area and should have been awarded a spot kick.

Neither incident was reviewed and the game finished 1-1, leading to the Brazilian FA making a formal complaint to FIFA today.

June 17 - Costa Rica v Serbia
VAR was called upon twice in injury time to look at disciplinary matters. It was ruled no offence was committed after a touchline scuffle involving Nemanja Matic over which team had the right to a throw-in.

Aleksandar Prijovic was then booked after catching Johnny Acosta in the face with his hand following another look at replays.

June 16 - Peru v Denmark
The South Americans were awarded a penalty after Gambian referee Bakary Gassama consulted the monitors to check whether Christian Cueva had been fouled by Yussuf Poulsen.

Cueva horribly miscued the spot-kick however, with Poulsen scoring the only goal of the game for the Danes.

June 16 - France v Australia
France benefited from a controversial first use of VAR technology at a World Cup as they laboured to a 2-1 win over Australia.

Antoine Griezmann put Les Bleus ahead with a contentious second-half penalty in Kazan after referee Andres Cunha adjudged the forward had been fouled by Joshua Risdon having watched a replay of the incident at the side of the pitch.

The RTÉ panel of Michael O'Neill, Louise Quinn, and Damien Duff discuss whether VAR decisions are taking too long.