Hundreds of cats a day are being rounded and crammed into cages so small they cannot even turn around.
Then they are trucked to what animal welfare groups describe as death camps on the edges of the city.
The cull comes in the wake of a government campaign warning of the diseases cats carry and ordering residents to help clear the streets of them.
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Cat owners, terrified by the disease warning, are dumping their pets in the streets to be picked up by special collection teams.
Paranoia is so intense that six stray cats -including two pregnant females - were beaten to death with sticks by teachers at a Beijing kindergarten, who feared they might pass illnesses to the children.
China's leaders are convinced that animals pose a serious urban health risk and may have contributed to the outbreak of SARS - a deadly respiratory virus - in 2003.
But the crackdown on cats is seen by animal campaigners as just one of a number of extreme measures being taken by communist leaders to ensure that its capital appears clean, green and welcoming during the Olympics.
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Secretive: The compound at Da Niu Fang which is patrolled by security guards
Polluting factories in and around the city are being ordered to shut down or relocate during the Games to ease Beijing's choking smog and drivers are allowed out on to the roads only three times a week.
Fares on the city's underground network have been cut to just two yuan (14p) for any journey - a six-fold reduction on some routes - to keep people off buses, and beggars and street sleepers are being moved to out-of-town camps or given train fares back to their home provinces.
Meanwhile, taxi drivers have been made to attend lessons in how to greet passengers politely in English and a city-wide courtesy campaign has been launched to teach Beijing's notoriously dour and grumpy citizens how to smile and be pleasant to foreigners.
The cull of Beijing's estimated 500,000 cat population is certain to provoke international outrage as it comes just over a year after the Chinese were criticised for rounding up and killing stray dogs across the country.
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Refuge: Campaigner Hu Yuan, 80, with some of the 250 cats she has taken in at her Beijing home
Animal welfare groups in China are already protesting, but their members fear punishment from the authorities.
Officials say people can adopt animals from the 12 cat pounds set up around the city, but welfare groups say they are almost impossible to get inside and believe few cats survive.
One cat lovers' group negotiated the release of 30 pets from one of the compounds in Shahe, north-west Beijing, but said they were in such a pitiful condition that half of them died within days of their release.
"These cats are being left to die. It is very inhumane," said the group's founder Yan Qi, who runs a sanctuary for cats.
A rescued pet showing clear signs of disease
"People don't want to keep cats in Beijing any more so they abandon them or send them to the compounds.
"When we went inside, we saw about 70 cats being kept in cages stacked one on top of the other in two tiny rooms.
"Disease spreads quickly among them and they die slowly in agony and distress. The government won't even do the cats the kindness of giving them lethal injections when they become sick. They just wait for them to die.
"It is the abandoned pets that suffer the most and die the soonest. They relied so much on their owners that they can't cope with the new environment.
"Most refuse to eat or drink and get sick more quickly than the feral cats."
Ms Yan's group has now been denied access to the pounds. "We do not believe any of the cats that go in there survive," she said. "They are like death camps."
Ms Yan said there was another reason for people abandoning their cats - the 200 yuan (£14) fee they face if they want to have their pets neutered and tagged.
"We have tried to negotiate with the government to stop the round-ups and to introduce cut-price neutering services so that people can afford to keep their pets but they won't listen to us," she said.
"They are not thinking about the cats. They just want to get results in the quickest way possible, by clearing as many cats from the city as they can."
Retired doctor Hu Yuan, 80, runs one of the few remaining refuges for abandoned pets in her ramshackle home in the ancient Long Tou Jing area of Beijing.
She shares her tiny home with 250 abandoned cats and has taken in 70 over the past 12 months alone.
She pays for neutering and food from her pension and donations. She said: "If I don't take them in, the government will kill them.
"People believe what the government tells them and that is why they are abandoning more and more family pets."
She said the problem could be traced back to former president Jiang Zemin for the crackdown.
"He didn't like dogs so he decided to have dogs killed. But there was a bad reaction from the foreign media and they were pressured to stop.
"Now they have stopped killing dogs but the new victims are cats. It is all connected to the Olympics."
Cats are regularly dumped on her doorstep late at night by owners frightened by the government campaign.
"The situation is very bad now," said Ms Hu. "When women get pregnant, the doctor will ask them if they have a cat in the house.
"If they reply Yes, they tell them, 'You must get rid of it, it will be bad for the baby'.
"I keep all the cats in my house and 100 of them sleep in my bedroom at night. I am too frightened to let them out. If they go outside, they will be taken away and killed.
"The government is not telling people the truth. Look at me. I live with them 24 hours a day, seven days a week and I am very healthy."
The round-up has been particularly intense in areas around Olympic venues and in streets and alleys surrounding five-star hotels where guests will stay during the summer games.
Despite the health warnings, the round-up of cats has led to a surge in the number of restaurants in the capital serving cat meat, according to Ms Hu.
She said hundreds of cats were also being sent to Guangzhou in southern China, an area infamous for restaurants that serve meat from cats and dogs and exotic animals such as snakes and tigers.
It was in July last year that district officials were instructed to begin an intense round-up of cats as part of Beijing's pre-Olympics clean-up. Now notices have been put up urging residents to hand in cats.
Welfare groups estimate that tens of thousands have been collected in the past few months.
The Mail on Sunday went to the cat pound in Shahe on the north-western fringes of Beijing but we were repeatedly refused admission.
"No one can come in without official papers," staff shouted from behind padlocked steel gates.
At another, larger compound in Da Niu Fang village, the sound of cats wailing could be clearly heard coming from a cluster of tin-roofed sheds, but workers denied they were holding any cats.
"There are no cats here, go away. No one is allowed inside unless you have official permission," a security guard said.
The killing of the six stray cats at the kindergarten - where staff at a Beijing cigarette factory leave their children - is the most striking illustration of the city-wide fear of cats.
A teacher at the nursery said: "We did it out of love for the children. We were worried the cats might harm them. These six cats had been hanging around the kindergarten looking for food.
"So three male teachers put out plates of tuna in cages for bait, trapped the cats and then beat them to death with sticks.
"We were very worried the children might try to stroke them and that the cats might scratch them or pass on diseases. We had to get rid of the cats and this was the only way to do it."
Christie Yang of the charity Animals Asia, which liaises with the Beijing animal welfare groups, said: "We are seriously concerned.
"We understand that with the Olympic Games the Beijing government is eager to show the world the city in a good light.
"But capturing and dealing with cats in such an inhumane way will seriously tarnish the image of Beijing and the Games."
• Names of the animal campaigners have been changed as the people we interviewed are concerned about officials' reaction to our story.