Under-pressure South Korea coach Jurgen Klinsmann has hit back at criticism levelled at him and his goalkeeper son for wanting the shirt of an opposition player, calling the flak "absolutely stupid".

The German legend reportedly approached Welsh captain Aaron Ramsey to ask for his shirt following a 0-0 draw in Cardiff between the home side and South Korea last week.

Former Germany captain and coach Klinsmann subsequently told British media that his 26-year-old son Jonathan, a goalkeeper for LA Galaxy, wanted the shirt.

With Klinsmann under pressure from South Korean fans following a fifth game without a win in charge, both father and son came in for criticism for the apparently innocuous gesture.

"It was for the physical therapist of my son's team in Los Angeles," the 59-year-old Klinsmann said after landing in South Korea late Thursday following a 1-0 win over Saudi Arabia in England, his first victory as coach.

"But to be honest, I don't understand why this would be a reason to criticise something," Klinsmann told reporters.

"I don't understand that to be honest because my son got critical comments on his Instagram, which is absolutely stupid."

Despite beating Saudi Arabia, Klinsmann is struggling to win over South Korean fans and media sceptical about his appointment in February.

As well as just one victory in six matches, Klinsmann has also been lambasted for failing to move to South Korea from his home in California.

He had been due to stay in Europe this weekend to see Korean players in action there, but changed his plans.

Asked for the reason behind the U-turn, the former striker told reporters: "Because you asked for it!

"The KFA (football association) asked if it's possible to come with the rest of the team, to see you, so I made changes and I go to see two games here, no problem."

Klinsmann attempted to turn the page on his poor start in charge and says the side is building nicely for the Asian Cup in Qatar in January-February.

"It's vital that everybody builds a positive spirit. The fans, the media, and the team obviously," he said.

"If it doesn't go well, there is enough time to criticise or fire the coach or do whatever you want to."