Olympic park security guards prevent journalists from filming venue Jason N Parkinson/reportdigital.co.uk

Private guards at the Olympic park have been filmed forcibly attempting to stop the media taking pictures and footage of the complex in east London, raising new concerns about potentially aggressive and over-intrusive security during the Games.

During the incident two guards from G4S, the security giant which is recruiting at least 10,000 staff for the event, attempted to clamp their hands over the lenses of stills and video cameras, even though the footage is being shot on public land.

While there are numerous rules about photography and filming inside the Olympic complex itself, which is private land, there are no restrictions on the use cameras from public areas.

Earlier this month the National Union of Journalists arranged a meeting with the two senior Scotland Yard officers in charge of Olympic security, in part to seek assurances that the media would not be harassed on public land.

Jess Hurd, whose camera was blocked by one of the G4S staff in the incident, said she had asked police about whether private security guards would be properly trained on photography laws. Police informed her that there should be no problems outside the venue.

"We were a bit bemused but thought we'd take it at face value. So we decided to have a walk round the perimeter," she said.

Hurd was among five photographers and video journalists who opted to walk around the perimeter of the Olympic site in Stratford, in part to take pictures of the preparations but also to test the security response.

As they walked along one pavement, near the adjoining Westfield shopping mall, a G4S guard approached the group and told them they were not allowed to film, before trying to hold his hand over Hurd's camera.

A supervisor who arrived told the group that guards had been specifically instructed to stop people filming a nearby "security screening area".

She said: "We are told that we should refrain from letting anybody film the security screening area. Obviously, we don't want that filmed."

The supervisor appeared not to know the difference between filming on public and private land, likening the rules to those against taking pictures of security checks at London's Heathrow airport.

She added: "We're all here for the protection of the Olympic park. Obviously, if you don't care about that, that's your business. We care."

At one point another guard made a lunge for a video camera in an apparent attempt to stop filming.

Hurd said she had been reassured by police at the meeting that private staff had been granted no extra powers for the Olympics, and that she was most baffled by the apparent instruction to prevent filming.

She said: "This is very significant, because obviously we were on public land. They've got no right to do that with anyone. At no point did they ask to see any ID, so whether we were professionals or not didn't come into it."

Last week media and civil liberties groups expressed surprise and concern after another venue which will host Olympic events this summer, the 02 arena in Greenwich, south-east London, said it instructed guards to routinely challenge anyone photographing or filming the structure, even on public land.

The response came after a Guardian reporter was stopped from shooting video footage from a pavement by 02 guards, who said they had powers to do this under terrorism laws.

A G4S spokesman said of Saturday's events: "We are looking into what happened. We are well aware of the laws permitting people to take photographs or film from public land."