Athens silver medallist Tatyana Tomashova is suspended
Russian Olympic officials have denied allegations that members of its team are involved in "systematic doping".
Some of the country's leading medal hopes have been expelled from the Games in the past week after failed tests and accusations of switching urine samples.
The head of the International Olympic Committee's medical commission, Arne Ljungqvist, said he had been frustrated by Russia's "planned cheating".
But Russian spokesman Gennady Shvets said it was too early to say that.
Shvets said: "It is strange that someone has said there is systematic doping. These situations are very unpleasant but to say it is systematic is premature.
"When in the United States they discovered the Balco laboratories, it was sad but they didn't say that the whole of US sport was involved in doping."
Seven Russian track and field athletes have been provisionally banned from Beijing, although only five, including 2004 silver medallist Tatyana Tomashova, were due to compete in the Games anyway.
Walkers Valery Borchin and Vladimir Kanaikin - a former world record holder - plus cyclist Vladimir Gusev, have also been dropped from the Games.
Ljungqvist, also vice-president of world anti-doping agency WADA, said: "This does seem to be an example of systematic planned doping, and under the new WADA code that would mean an expanded ban of four years.
"The federation have done a very good job in revealing a very bad doping story which is just frustrating to find.
"It's sad and very disappointing."
When I line up next week, I will
look left and right and know the other girls aren't all clean
Tamsyn Lewis, Australian 800m competitor
Meanwhile, Australian officials have advised outspoken runner Tamsyn Lewis to keep her opinions to herself and concentrate on her events after she launched a blistering attack on Olympic drug testing.
Lewis, the world indoor champion for 800 metres, said she
had become completely disillusioned with athletics because she believes her sport is riddled with drug cheats.
"I have got to the point where this is just farcical and
simply unfair on the athletes who are clean and get there on
their own merit," she told Sydney's Daily Telegraph from her
training camp in Darwin.
"I have no doubts that when I line up next week, I will
look left and right and know the other girls aren't all clean. That is such a disgrace and I've lost all faith in the
system because there are so many athletes who are slipping
under the radar."