Germany boss Hansi Flick has conceded that his side "are under pressure" at the World Cup following their 2-1 defeat to Japan in their Group E opener on Wednesday.

Ilkay Gundogan sent the four-time world champions ahead from the penalty spot in the 33rd minute, but Japan turned the game around in the second half, levelling through Ritsu Doan before Takuma Asano won it late on.

Germany are currently third in Group E ahead of Sunday's clash with Spain, who opened their tournament with a 7-0 victory over Costa Rica.

Flick refused to play down the importance of the game against La Roja while admitting his disappointment with his team's performance against Japan.

"Of course with this defeat and zero points, we are under pressure, there's no question about that," Flick told reporters after his side's shock defeat.

"We can only blame ourselves – we have to make sure we can come out of this, we have to be courageous, we need the aggression in the game that's necessary at a World Cup.

"It's a great disappointment. We were on the right path in the first half, we had 78% possession and were ahead, then we had good opportunities in the second half and didn't take advantage of them.

"Japan were simply more efficient today - we made mistakes we should never make, especially at a World Cup. I'm pretty sure we can do better - we have to do better. We have the quality, but we have to keep it up for 90 minutes. It's a missed opportunity and a bad start for us."

Germany won the World Cup in 2014, but they failed to make it out of the group in 2018, losing two of their three matches during that particular campaign.

Gundogan was also critical of his side's performance against Japan, with the midfielder claiming that DFB-Team 'lacked conviction with the ball'.

"There was a bit of a lack of conviction with the ball - from behind," he told reporters. "Holding the ball, moving, offering.

"And we relied too much on long balls in the second half. And the short ones we played we lost too easily. You felt that not everyone really wanted the ball. We lost the ball way too often and way too easily."

Germany, who have two more fixtures in Group E against Spain and Costa Rica, have now been victorious in just one of their last four matches in all competitions.