BEIJING (AP) — Don't roll down the taxi windows. Don't buy a remote-controlled plane without a police chief's permission. And don't release your pigeons.

Beijing is tightening security as its all-important Communist Party congress approaches, and some of the measures seem downright bizarre. Kitchen knives and pencil sharpeners reportedly have been pulled from store shelves, and there's even a rumor that authorities are on the lookout for seditious messages on pingpong balls.

The congress, which begins Nov. 8, will name new leaders to run the world's most populous country and second-largest economy for the next decade. Most of the security measures have been phased in in time for Thursday's opening of a meeting of the Central Committee, the roughly 370-member body that is finalizing preparations for the congress.

China always tightens security for high-profile events, like much of the rest of the world. London, for instance, restricted air traffic during the Olympics.

But many of Beijing's rules seem extraordinary, perhaps in an effort to smooth a once-a-decade transition that has already been bumpy.

Bo Xilai, once a candidate for the all-powerful Politburo's Standing Committee, suffered a spectacular fall from grace in which his wife was convicted of murder. One of President Hu Jintao's closest aides was demoted, apparently after his son was killed alongside two partially dressed women in an accident in his Ferrari. Meanwhile, protests over pollution, land seizures and local corruption continue across the country.

Human rights groups report that activists and petitioners are being rounded up ahead of the congress. But the broader security measures may best illustrate how China is trying to leave absolutely no room for disruptions.

The government has blocked searches for the phrase "18th Party Congress" on websites including China's popular Twitter-like Sina Weibo. Internet posters manage to get around that by using characters that sound like "party congress." One substitute: "Sparta."

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Taxi drivers have been told to remove window handles, to avoid sensitive parts of the city and not to open their windows or doors if they pass "important venues." Some taxi drivers, but not all, have been told to ask passengers to sign a "traveling agreement" if they want to go near Tiananmen Square.

A man who answered the phone at Wan Quan Si taxi company in the south of the capital said the rule applies to all taxi companies in Beijing. He declined to give his name.

Beijing investment company worker Li Tianshu said she didn't believe colleagues' claims that door handles had been removed until she got into a taxi herself the other day.

"There were no handles for three of the four windows," she said. "The driver told me that their company asked them to do it to prevent passengers spreading leaflets. The driver complained that if they don't take the handles away or the passengers throw leaflets out of the taxis, they will be fired."

Citizens have taken to Weibo to post photos of doors with handles crudely ripped off. Liu Shi, a client manager in a mass communication company, wrote that the taxi driver had told him that power to electronic window buttons would also be cut.

A memo circulating on Weibo warned taxi drivers to be on guard against passengers who may want to cast balloons with slogans or throw "pingpong balls with reactionary words." It was unclear who issued the memo and its authenticity could not be confirmed.

A man who wouldn't give his name at Tong Hai taxi company in central Beijing said it had received orders "from higher authorities" to reinforce security measures and a memo, but he wouldn't elaborate.

Police in the capital are asking that Chinese show their ID cards and foreigners their passports when buying remote-controlled model aircraft over safety concerns, the official Global Times newspaper reported Tuesday.

One toy store owner said authorities had told him to stop selling medium and large-sized planes.

"This kind of plane can't fly over long distances and it can hardly carry anything," said Chen Ziping, holding up a model about half a meter (half a yard) long. "They just told me to stop selling it and I have to follow the order."

The Global Times quoted an unnamed police officer from Aoyuncun station in Chaoyang district as saying that people wanting to buy model planes during the congress should go to the vendor's local police station to register. When the buyer receives approval from the station's police chief, he can make the purchase, the officer said.

Still, they won't be allowed to fly model planes in the city, and balloons also are on the blacklist, the newspaper said. It cited another officer from Chaoyang district Public Security Bureau as saying that pigeon owners must keep their birds in their coops during the congress.

Chen Jieren had a run-in with the security rules Sunday after the handle of his knife broke while he was cooking dinner. He took his ID card to the supermarket, knowing that people must show identification when buying knives during sensitive periods.

"Well, it didn't work this time," Chen said in a telephone interview. "I was told by the police that no more knives can be sold, not even pencil sharpeners. And I don't think the shopkeeper was kidding, because several days ago I saw myself that police were asking the sales assistants in the stationer's not to sell pencil sharpeners.

"I went back and got an old knife and tried to sharpen it. I guess I have to live with it until the Congress finishes," he added, glumly.

Wang Ye, an engineer from Beijing who lives in Shanghai, was planning on returning to his home city to run a marathon, but it was postponed with no word on when it might be held. The date of a marathon in the eastern city of Hangzhou, near Shanghai, was also changed.

"There is no official explanation, but we all know that it is due to the 18th Congress," he said. "(The Beijing marathon) has been held regularly for the past 31 years.

"I guess I will give up running competitions in China and try to attend more abroad," said Wang. "At least they tell me the schedule one year before the event."