Police have apologized to the family of a 27-year-old man beaten to death by gangsters in March, admitting they mishandled the case, a local police station chief said Thursday.

Azumao Tanaka, head of Kobe West Police Station, revealed that he and another police official visited Kuniaki Uranaka's family on March 26 and apologized for failing to take appropriate steps in the initial phase of the investigation.

They promised his mother they would open a full probe into the slaying.

"I want police to learn from this case and improve the quality of their investigations," she said.

Uranaka, 27, a graduate student at Kobe University of Mercantile Marine, is believed to have been abducted and beaten to death by gangsters affiliated with Yamaguchi-gumi, the nation's largest crime syndicate, on March 4.

Police have so far arrested nine mobsters in connection with the case.

Criticism of the police has been mounting over their failure to act, even after receiving three phone calls, including one from Uranaka himself, during which they were given information that he may have been abducted.

Police are conducting an in-house probe into the case.