SINGAPORE—Singapore authorities said Friday that the Singaporean man allegedly leading a global soccer match-fixing syndicate has been cooperating with police investigations.

Dan Tan Seet Eng "is currently assisting Singapore authorities in their investigations," Singapore police said in response to queries. It didn't elaborate on how Mr. Tan is assisting police or whether he has been detained.

European investigators say they believe Mr. Tan is the leader and financier of a crime syndicate allegedly responsible for fixing hundreds of soccer matches around the globe. Mr. Tan couldn't be reached for comment.

Singapore's announcement came as Italian police arrested a Slovenian man suspected to be a member of this crime syndicate. Admir Suljic, who turns 32 years old on Saturday, surrendered to police at Malpensa international Airport west of Milan early Thursday, Italian police said.

This month, Europol, a coordinating group for European police forces, said had evidence that 680 soccer matches played around the world—including in some of the sport's biggest tournaments—may have been fixed. Some 425 soccer and team officials, players and others are suspected of being involved, and dozens have been arrested.

Europol said it uncovered more than $10.9 million in alleged betting profit and at least $2.7 million in corrupt payments to people involved in the matches believed to be have been fixed. A Europol official said Mr. Tan was one of the people being investigated in this probe.

Write to Chun Han Wong at