The German Football Federation has opened an investigation after Werder Bremen striker Claudio Pizarro appeared to slap Hannover defender Emanuel Pogatetz in a Bundesliga match.

The DFB says referee Christian Dingert failed to see the alleged case of ''extreme sporting misconduct'' in the 49th minute of Bremen's 3-0 Bundesliga win over Hannover on Sunday.

The incident was picked up on TV, showing the 33-year-old Peru striker catch Pogatetz's right cheek with the palm of his left hand.

Pizarro apologized to the Austrian international after the game, telling Sky TV that ''I was trying to push his hand away. I never wanted (to slap him).''

Pizarro scored one goal, his 16th of the season, and set up another in the game.