Security stepped up for Independence Day

Security at Wimbledon will be stepped up today amid fears that American players and supporters visiting the championships may be targeted by terrorists for an Independence Day attack.

The Metropolitan Police said that, though they had received no specific threats against the players, the operation was in line with advice being offered to US banks, hotels, corporations and prominent individuals this week.

US corporations and citizens have been warned that traditional parties to mark the event could be "soft targets" for suicide bombers and kidnappers and have been advised to remain vigilant. A party thrown by the American ambassador William Farish, who visited the royal box yesterday, at his residence in Regent's Park, London, will also be the focus of heightened security.

About 40,000 people are expected to attend the championships today, many of them drawn by the prospect of seeing the leading US women players contest semi-finals.

Venus Williams is scheduled to play Justine Henin as she aims for a third successive title, and her sister Serena, the French Open champion, will seek to reach her second successive grand slam final against Amélie Mauresmo.

A Scotland Yard spokesman said that extra police would be on duty near potential targets in London and wherever Americans were likely to gather in large numbers. They said they were aware of the potential threat to Wimbledon.

"Whilst there is no specific threat for July 4, our concern does remain high. This situation will be kept under constant review and additional policing can be introduced if deemed necessary."

A spokesman for the All England Club said yesterday: "Security will be beefed up. There was a security exercise operation for services personnel this morning and we are reviewing procedures. We are aware that July 4 has special connotations and we will take appropriate measures."

Today's operation comes after several embarrassing breaches of security at the All England Club since the tournament began 10 days ago.

This week three people have entered the players' lounge without being challenged despite the presence of more than 1,000 stewards and service personnel.

Last week the prankster Karl Power and a friend leapt on to centre court and played a rally shortly after Monica Seles had finished a match. In 1993 Seles was stabbed in the back by a deranged fan during a match in Hamburg, Germany.