TOKYO, Oct. 17 - Prime Minister Junichiro Koizumi's visit to a nationalist war memorial here drew immediate and fierce criticism from Asian countries today, threatening to isolate Japan in the region and deepen its already strained relations with China.

Beijing condemned the visit to the memorial, the Yasukuni shrine, as "a serious provocation to the Chinese people," and canceled bilateral talks on the North Korean nuclear crisis scheduled for today. South Korea also announced that it would cancel or postpone a trip to Japan scheduled for December by President Roh Moo Hyun, citing the shrine visit.

After months of speculation about the timing of this year's visit, Mr. Koizumi this morning fulfilled his promise of praying annually at the memorial. The Shinto shrine, which deifies Japan's 2.5 million war dead, including Class A war criminals responsible for atrocities throughout Asia, is regarded by most Asians as the symbol of unrepentant Japanese militarism.

"Prime Minister Koizumi has to bear the historic responsibility for damaging China-Japan relations," China's ambassador to Japan, Wang Yi, said in a statement.

In Seoul, a presidential spokesman, Kim Man-Soo, said that the South Korean government was no longer planning for a summit meeting in December or one-to-one talks between the two leaders at next month's Asia-Pacific Economic Cooperation meeting in Pusan, South Korea.

At a tense summit meeting in Seoul last June, President Roh told Mr. Koizumi that the visits to Yasukuni lay at the "core" of problems between the two nations. Until early this year, relations between Japan and South Korea had improved to such an extent that two summit meetings had been planned annually, one in each country.

The visit also drew protests from Taiwan and Singapore, two other nations that suffered under Japanese militarism. The leaders of the Yasukuni shrine and its museum have long stood at the center of a movement to justify Japan's prewar conduct. Their argument is that Japan tried to liberate Asia from Western powers and was pushed into World War II by the United States, and that war criminals enshrined there were innocent.

As Mr. Koizumi has led Japan to adopt a more assertive foreign policy, more and more politicians and public figures have also been openly trying to justify Japan's past. Their message has resonated in a country where anxieties over a shrinking population, uncertain economic prospects and China's rise in power have led to an increase in nationalist sentiments.

Mr. Koizumi rejected criticism of his visit, saying that he was merely paying homage to Japan's war dead.

"From a long-term perspective, I believe China will understand," Mr. Koizumi said. "No foreign government should criticize the way we mourn our war dead."

Mr. Koizumi, who arrived at the shrine in his official car, was flanked by a phalanx of bodyguards, and was seen praying in live broadcasts across the nation. He said he visited the shrine as a private citizen.

To downplay his visit's significance, Mr. Koizumi wore a gray suit, in contrast to the formal wear of his previous visits. He also refrained from entering the inner shrine and did not follow the precise Shinto ritual of bowing and clapping.

"It is extremely regrettable that the prime minister offered prayers at Yasukuni shrine where Class A war criminals are enshrined," said the leader of the main opposition Democratic Party, Seiji Maehara. "I think he should surely be aware that the prime minister, as a public official, cannot distinguish the official from the private."

Mr. Koizumi's muted visit, though, appeared to be a concession to growing criticism at home, with most polls showing the public opposed to his continued visits.

Takenori Kanzaki, the leader of the New Komeito Party, the governing party's junior coalition partner, told reporters that Mr. Koizumi probably took into consideration a ruling last month by the Osaka High Court that his visits violated Japan's constitutional separation of religion and the state.

It was perhaps also a slight concession to Japanese business leaders, who have openly criticized his visits and had dreaded any future ones. While Japan's political leadership has tended to regard an increasingly powerful China as a threat, its business leaders see it as an opportunity. Indeed, the Japanese economy has revived recently thanks in great part to China.

Hiroshi Okuda, the chairman of Toyota and of Nippon Keidanren, Japan's powerful business association, said in a statement that the prime minister had given consideration to domestic and international affairs by visiting the shrine as a private person. Both organizations strongly supported Mr. Koizumi in last month's general election.

But Kakutaro Kitashiro, the chairman of the Japan Association of Corporate Executives, another powerful association which supported Mr. Koizumi last month, was more critical.

"His visit has drawn criticism from our neighboring countries," Mr. Kitashiro said in a statement. "So we hope that he will fully recognize that it might damage our national interest, that careful explanations must be given to our neighboring countries and that diplomatic efforts must be made to gain their understanding."