The Chinese government has sent tanks to watch over the Olympic media centre in an extraordinary show of force as they tighten their control over their own journalis
The move, which was imposed over the heads of the Beijing Olympic Committee, was a vivid illustration of the continuing power of the Communist Party even as the country has been opened to unprecedented from the outside world.
It followed a letter sent to the editors of all newspapers in the country containing 21 rules for reporting during the Olympics.
The letter, leaked to The Daily Telegraph, lays particular stress on anything to do with foreigners and is clearly aimed at preventing any events that undermine the show of national unity that has surrounded the Games being released to the general public.
The armoured personnel carriers, unprecedented at recent Games, were stationed at either end of the main press centre, one of a number of increased security measures put in place around Beijing. Armed police stood with sub-machine guns in key areas, including at the press centre entrances.
They appeared to come as a surprise to the Beijing Olympic Committee, which said it had not been made aware of the reasons for the action.
Police have warned of the threat to the Olympics of terrorism, particularly from the ethnic muslim Uighurs of the far west, which has seen three major terror attacks in the last nine days.
But it was noticeable that the tanks were not protecting the stadiums or other venues likely to see large numbers of members of the general public.
While their guns were covered, they contained troops and their presence, inside the inner security cordon on the Olympic Green through which only accredited journalists had access, seemed more targeted at the reporters, including Chinese ones, working at the centre.
The authorities are concerned that major security incidents that threaten foreigners, and particularly the all-important foreign investment, might form a toxic reaction with both nationalist and liberal sentiments in newspapers. Local journalists are operating alongside a larger foreign media presence than at any time in China's history.
In recent times China has been reluctant to show off on the streets the military power that underpins its rule, particularly since the Tiananmen Square massacre of 1989. No Red Square-style military parades have been held since the 50th anniversary of Chairman Mao sweeping to power in 1999.
The mobilised units come from the People's Armed Police, the troops entrusted with internal security. They formed the bulk of the armed force sent to put down protest in Tibet in March, as well as providing the famous blue-suited "Olympic Torch" guards seen on the streets of London and Paris in April.
It is not clear what precise connection they have to recent events such as the killing of Todd Bachman, the father-in-law of a US volleyball coach, by a lone assailant at the historic Drum Tower in northern Beijing.
The authorities have been keen to say that the attack was "not related to the Olympics" and was the work of a man who had suffered a series of failures in his business and personal life. Local newspapers have been told to provide only brief reports, which must not mention the Games.
Chinese reporters who attended a press conference with the US volleyball team later had their notebooks and tape-recorders removed by officials.
But there were reports in Hong Kong that the man had a long-term grievance against the authorities. His choice of the Drum Tower may also have had symbolic importance - in the 1920s it was renamed the Tower of Realising Shamefulness and used to house exhibitions illustrating China's grievances with western powers.
In any case, the fact that the attacker was able to inflict such damage on a foreigner, and had time to then commit suicide without being apprehended, would have triggered nerves through the leadership, which has prided itself on its tight security controls throughout the city.
Chinese media will also be aware, as many foreigners are not, that nationalist sentiment often gives way to anti-government protest in China.
The list of 21 rules for covering the Olympics shows how far the party is prepared to go in asserting its rule, and especially its control over the media.
Many are only to be expected - bans on writing about pro-Tibet protesters, or about the internet curbs that were relaxed in Beijing after visiting journalists and the International Olympic Committee protested.
But on all matters to do with foreign affairs, the party line must also be followed closely.
Some are unusually specific: "In case of an emergency involving foreign tourists, please follow the official line," says number 17. "If there's no official line, stay away from it."
It also warns against hyping nationalist expectations over the Games. Journalists are banned from making medal predictions - which might not be met - and its final instruction is unequivocal.
"Refrain from publishing comment pieces at odds with the official propangada line of the Chinese delegation," it says.----------From the Vancouver Sun Blog:
Miro Cernetig, Columnist
I don't know whether to feel safe or very worried.
There's a helicopter flying over Tiananmen Square.
This is very, very strange. It's the most restricted airspace in China. In all the years I've lived here, I've never seen anything other than a kite flying over Tiananmen. But today there's been a helicopter doing low altitude passes around the square and on the streets leading to it.
It has an amazing effect below. You don't often hear planes or jets or helicopters over downtown Beijing. So when you do, people stop eating, stop talking, stop drinking and head to a clear spot and look up. What they now see is a very big helicopter doing slow passes. It started a few days ago. But there are more today than ever before.
I assume it's China's security forces telling everyone below that they are watching and ready to squash anything that will stain the games.