Russian referee Valentin Ivanov said the stormy World Cup match between Portugal and Netherlands was the most difficult of his professional career.

Ivanov has been under fire for his performance in Sunday's second-round clash, won 1-0 by Portugal, which saw a World Cup record four red cards shown.

"Probably, from the point of view of rudeness, it was the worst match I ever had," the 45-year-old referee said.

Both teams finished the bad-tempered encounter with nine men while eight others were cautioned.

Ivanov, who will end his international career this year because of FIFA's imposed age limit of 45, defended himself.

Asked if he thought he had made any mistakes, he said: "I don't know. I haven't seen the video yet but I called the action as I saw it."

Ivanov said he was taken by surprise by the rough tactics of Dutch players.

"You would expect some dirty tricks from the Portuguese. They are known for time-wasting or hitting from behind," he said. "But I was unpleasantly surprised by seeing such things from the Dutch. More so, they were the instigators."