Private security guards manning venues at July and August's London Olympics have been warned against over-zealous behavior that might alienate sports fans, the firm in charge of training said on Thursday.

Guards salute Queen Elizabeth during the Diamond Jubilee Parade and Muster in Windsor, England, May 19, 2012. [Photo/Agencies]

The opening day of a major event can be tense, as the start of the Olympic torch relay demonstrated this week when a police security team escorting the runners grabbed a spectator they thought was trying to reach the torchbearer and pushed him into a hedge.

Mark Hamilton, the man leading G4S's Olympic security team which will operate airport-style searches and screening at venues, said guards were being encouraged to engage with spectators.

"I think it is very relevant not to over-react to situations that arise on the first day - to make sure they are properly assessed and that the communications process is working in the way it should so that the decisions are made at the right time and people act in the right way," the managing director told reporters.

He said guards had to be thorough but it should not be an "onerous experience" for fans.

He suggested guards may have acted over-the-top when stopping photographers taking pictures from a public path of a vehicle checking area in the Olympic Park.

"There's no doubt that's a lesson learnt, not to overly criticise the workforce and the guards involved because they are operating under a regime where hostile reconnaissance is something they have to be aware of," he said.

"How they handle that, and how they manage it and how they report it is obviously something we've learnt a lesson from."

G4S guards can also check vehicles, such as buses, travelling through the Olympic Park in east London.

More than 100,000 people applied for one of the 10,400 temporary jobs in what G4S describes as one of the biggest paid recruitment drives in Britain this century.

G4S will recruit, train and coordinate the guards, in addition to managing 3,300 students and 3,000 volunteers.

As well as screening at entry, guards will be responsible for queue management and protecting the perimeters and equipment.

The London Olympic organizing committee (LOCOG) was forced to renegotiate its contract with G4S at the end of last year after the committee more than doubled the number of people needed from an early estimate of 10,000 to 23,700.

The cost went up from 86 million pounds ($135.15 million) to 284 million pounds, leading to criticism in a UK parliamentary spending watchdog report.