Argentine tennis star David Nalbandian received a maximum fine and was placed under police investigation for assault after kicking a board and injuring a line judge during Sunday's championship match at London's Queen's Club.

The ATP confirmed the $12,560 fine for Nalbandian's unsportsmanlike conduct and said the Argentine was also stripped of his $57,350 runner-up prize money.

London police are investigating an assault complaint filed against Nalbandian, who was disqualified from the Queen's Club final against Croat Marin Cilic.

Police did not say who filed the complaint. The line judge, Andrew McDougall, could file a complaint, as could any member of the public who witnessed the unfortunate event.

"We are aware of an incident at the Aegon Championships," the Metropolitan Police said. "A complaint has been made and the Metropolitan Police Service is now investigating. The allegation is of assault."

Nalbandian, who had won the first set Sunday against Cilic, lost his cool after missing a running forehand, which caused him to lose his serve and fall behind 3-4 in the second set. He then kicked a small advertising board on the court in front of McDougall's chair, and McDougall received a bloody inch-long cut on his left shin as a result.

Nalbandian was then disqualified.

ATP rules state that any violent action will result in an automatic default.

Nalbandian insisted he shouldn't have been disqualified.

"Sometimes you get very frustrated on court and it's tough to control that, and sometimes I do a mistake. So it's very tough to end a final like that," he said. "I agree I do a mistake, but sometimes everybody do a mistake and I didn't feel it had to end like that, especially in a final."