Liverpool manager Juergen Klopp said there is no point raising complaints with Premier League referees as it is like speaking to a microwave, with the German left fuming by the officiating in their 3-1 defeat at Brentford on Monday.

Klopp said Brentford were "stretching the rules" with their pushing and holding, especially at set-pieces, and thought Bryan Mbeumo's third goal should have been ruled out for a foul.

When asked whether he had spoken to the match officials about the issue, Klopp told beIN Sports: "Yeah, but actually that's exactly the same as I would talk to my microwave, you get no response, really. It's always the same.

"Before the season they gave us advice that the players have to be careful in these moments because the refs will have an eye on it. You see in these games pretty much everything is allowed, it's always on the edge and they are using it."

Virgil van Dijk was one of three Liverpool players to come off at halftime but Klopp confirmed the defender was substituted due to a niggle, while the other two - Harvey Elliott and Konstantinos Tsimikas - were for tactical reasons.

"Virgil felt a little bit the muscle and said it is fine, and he is a very good judge of these kind of things. But I didn't want to take any risks," Klopp said.

"The physios looked quite happy when I said we don't take risks. It's not an injury, he just felt the intensity."

Liverpool remain sixth in the league, four points behind fourth-placed Manchester United, who have played a game less.