TAIPEI (AFP) - Taiwan police have arrested 45 people involved in a betting ring worth more than US$40 million (S$57 million) a year including wagers on the upcoming elections, officials said Monday (Jan 4), adding the racket could have influenced voting.

Police launched weekend raids on 31 venues across the island and made the arrests on charges of gambling and obstructing votes, prosecutors said.

"As the ring had so many posts islandwide and so many gamblers were involved, we fear that the gambling could influence the outcome of the election," said Wang Yi-wen, spokesman for the Taoyuan Prosecutors' Office.

Taiwan holds presidential and parliamentary elections on Jan 16.

Gambling is banned in Taiwan, apart from lotteries run by authorised banks. But there is a vast underground network involving private casinos, pigeon-racing and bets linked to Hong Kong horse-racing.

Investigators said gamblers were betting via the ring on the outcome of the elections as well as on sports and on an illegal lottery, using phone and fax lines, mobile phones and online.

They estimated around Tw$1.4 billion (S$60.4 million) had been wagered through the ring last year, but it was not immediately clear how much of it was related to the elections.

The ringleader was named as Lin Shih-yuan and remains in custody. Fifteen others have been bailed and 29 more released under restrictions, prosecutors said.

Wang said the crackdown was part of efforts to fight election gambling, vote-buying and violence, which have dogged politics in Taiwan.

Government figures showed that before local elections in 2014 more than 2,400 people were investigated for vote-buying - both candidates and supporters and mostly in rural locations.

According to prosecution statistics 601 people are currently being investigated for vote-buying in 337 cases related to January's vote.