British police have warned ticket touts who haunt major sporting events that they face "the most hostile environment ever" if they try to ply their trade at the Olympics.

Nick Downing, leading efforts of British police to combat ticketing crime at next month's Games, also told sports fans to only come to London if they had bought tickets from an official supplier.

Attempts to clean up the process received a setback last week when The Sunday Times newspaper reported that National Olympic Committees and Authorised Ticket Resellers representing more than 50 countries had broken the rules on the sale of tickets.

Downing said the police were assessing material obtained by the newspaper and had discussed the issue with the International Olympic Committee (IOC) and London organizers.

Having previously warned of the danger of online scams, police are now delivering a tough message to touts who offer to "buy or sell" tickets outside venues and have been an unloved part of the British sporting scene for decades.

"We will target you. It will be the most hostile environment you have ever been in," Downing said.

Downing added that British touts would be operating in Ukraine ahead of England's Euro 2012 quarter final with Italy in Kiev on Sunday.

"We know what they are doing. We are working at Wimbledon next week to deter them," he told Reuters in a telephone interview, referring to the highlight of the British tennis calendar.

Britain has increased the fine for illegal ticket sales to 20,000 pounds ($31,500) from 5,000 under legislation brought in ahead of the Olympics.

Police are investigating 30 unauthorized online sites dotted around the world which claim to be selling Olympic tickets, some based in Europe and others in the United States.

Downing said some were "out and out fraud", set up simply to harvest bank account details from unwitting fans. Others would not be able to deliver the tickets they were promising to sell.

"We don't want people to book flights and accommodation on the basis they are getting tickets," said Downing, who leads the police's "Operation Podium".

"A key message from me would be, unless you have your ticket, don't travel."

Tickets for the July 27-August 12 Games have begun to arrive at British homes. Demand for many events has outstripped supply, causing frustration over the way tickets have been allocated.

(Reporting by Keith Weir, Editing by Tom Bartlett)