BEIJING — The International Olympic Committee and China clashed yesterday over human rights and the protest-plagued Olympic torch relay. IOC president Jacques Rogge acknowledged that the Olympics have plunged into crisis, then pleaded with China to respect its promises on human rights.

But China immediately lashed back, demanding that the IOC refrain from “irrelevant political factors.” It also extended its security crackdown, arresting dozens of people in an alleged plot to kidnap foreigners and disrupt the Olympics.

The sharp exchange over human rights was a dramatic escalation in tensions between Beijing and the IOC, which had patiently avoided any direct criticism of China despite weeks of turmoil in Tibet and on the Olympic torch relay route.

The comments by Mr. Rogge, who was in China to meet with Premier Wen Jiabao to discuss preparations for the Beijing Games, were his strongest since the wave of Tibetan protests began last month. Up to that point, in fact, he had insisted that the IOC was powerless to exert any influence over China.

Yesterday, for the first time, Mr. Rogge referred explicitly to China's unofficial promises in 2001, when its leaders proclaimed that its human-rights record would improve if it won the right to hold the Olympics.

“We definitely ask China to respect this moral engagement,” he told reporters in Beijing.

He acknowledged that Olympic athletes were in “disarray” and the torch relay was “not the joyous party that we had wished it to be.” He said he was “saddened” by the violence in Tibet and the chaotic protests during the torch relay in London and Paris this week.

The torch arrived yesterday in Buenos Aires, its only South American stop, where nearly 6,000 police and other guards will protect the torch route today. “It is a crisis, there is no doubt about that,” Mr. Rogge said. “Athletes in many countries are in disarray and we need to reassure them.”

But a spokeswoman for the Chinese Foreign Ministry swiftly fought back, telling the IOC to stick to sports issues. “I believe IOC officials support the Beijing Olympics and adherence to the Olympic charter of not bringing in any irrelevant political factors,” said Jiang Yu, a Foreign Ministry spokeswoman.

“I hope IOC officials continue to adhere to principles of the Olympic charter,” she told reporters yesterday.

The exchange between Mr. Rogge and the Chinese Foreign Ministry has put a spotlight on the promises that China made in 2001, when it was lobbying for the right to hold the Olympics.

Just before Beijing won its bid for the Games, senior Chinese officials promised that any protesters, including Tibetans, would be free to voice their opinions. “You can apply to demonstrate and the police will give you a time and place,” said Wang Wei, secretary-general of the Beijing bid committee, at a press conference in 2001.

“A successful bid would improve all facets of life in China, including education, health and human rights,” he said.

The same promise was made by Liu Qi, mayor of Beijing. “Hosting the Games will help promote our economic and social progress and benefit the further development of our human rights,” he said in 2001.

After winning the Olympics, the Chinese government has backed away from these promises, insisting repeatedly that the Olympics is merely a sporting event that should not be “politicized” with other issues.

With the Olympics approaching, China has been cracking down on dissent of all kinds, imprisoning dissidents, tightening control of the media and imposing “patriotic education” classes on Tibetans and other minorities.

Yesterday the Chinese security agencies announced the arrests of 45 people in two “terrorist” cells in Xinjiang, the predominantly Muslim region of Western China. The suspects were accused of plotting to disrupt the Olympics by bombing hotels, poisoning food and kidnapping foreign journalists and other foreigners.

A police spokesman said explosive vests were seized in police raids in Xinjiang over the past three months, suggesting that the detainees were planning suicide attacks.

The latest arrests suggest that China will continue its hard-line stand in Tibet and other ethnic areas, using the terrorism allegations as another justification for its crackdown, according to Willy Lam, a political analyst based in Hong Kong.

China's state media have recently begun to describe Tibetan activists as terrorists. The arrests in Xinjiang will create the impression that the security crackdown in Tibet and Xinjiang is part of a national anti-terrorism campaign, Mr. Lam said in an interview yesterday.

Tibet's exiled leader, the Dalai Lama, repeated yesterday that he supports the Olympics, despite Chinese claims that he is sabotaging the Games. “I really feel very sad that the government demonizes me,” he told reporters in Japan as he headed to the United States for his first visit since the Tibetan crisis began.

“I am just a human; I am not a demon,” he said.

China should not tell Tibetans to “shut up,” he added.