China and South Korea both lashed out after Koizumi, dressed formally in "hakama" pleated skirt and traditional "kimono" bearing his family crest, walked solemnly into the Yasukuni Shrine to mark New Year's Day.

Honouring 2.5 million Japanese war dead, Yasukuni is widely seen as a symbol of Japan's former militarism, particularly since 1978 when it enshrined 14 war criminals including wartime prime minister General Hideki Tojo.

Koizumi bowed deeply at the main chamber before being escorted inside by a Shinto priest to pay his respects out of sight from the media.

"I prayed for peace and prosperity in Japan ... which has been built based on the people who lost their lives against their will during the war," Koizumi told reporters.

Defending the visit to the war shrine, he said: "No country interferes in other countries' respect for history, tradition, custom. Since I am visiting here every year, I hope to gain understanding gradually."

But Koizumi's words cut no ice with China and South Korea, where bitterness over Japan's brutal occupation of both in the 20th century remains deeply ingrained.

Beijing and Seoul voiced strong anger at Koizumi's fourth visit to the shrine since he took office in 2001 and his first pilgrimage on a New Year's Day, Tokyo's most important national holiday.

Summoning the acting Japanese ambassador, China's Vice Foreign Minister Wang Yi expressed "righteous indignation" over the visit, which he said had taken place "regardless of the opposition of the peoples of China and Asia".

In Seoul, the foreign ministry said: "It is really hard to understand that Japan's highest government official continues to pay homage to those war criminals. We cannot but express anger as well as anxiety as it hurt the feeling of our people again."

Japan colonised the Korean peninsula between 1910 and 1945.

Koizumi is only the third prime minister since 1978 to visit the shrine adjacent to the Imperial Palace in central Tokyo.

The nationalist premier has pledged to make a pilgrimage once a year to "dedicate on peace" but has avoided visiting on sensitive days such as August 15, the anniversary of the end of World War II.

Commenting on the reason for visiting the shrine on New Year's Day, Koizumi said he followed "Japanese tradition", adding: "I had been wondering when I should visit. I made the decision today and it was a good choice."

The opposition camp and even some ruling lawmakers criticised the visit.

"His personal belief is damaging national interest," said Naoto Kan, leader of the largest opposition Democratic Party of Japan. "This is not responsible behavior toward the people."

Takenori Kanzaki, head of the New Komeito party, the Buddhist-backed ally of Koizumi's Liberal Democratic Party, said: "It was regrettable as it may be taken as violating the Constitution."

The visit may further fuel criticism of Japan's planned dispatch of some 1,000 troops to Iraq.

An advance party from its self-defence military contingent left for the Middle East on December 26 to set the stage for a humanitarian mission in the war-torn nation.

The deployment represents the first time since World War II that a Japanese military unit will be sent to a country where fighting is still raging. Japan's post-war constitution bans the use of force in settling international disputes.

Koizumi's pilgrimage may also dampen efforts for closer cooperation with Beijing and Seoul to confront the North Korean nuclear crisis.

China plans to host a second round of six-nation talks over the crisis in January, inviting officials from the North and South as well as Japan, Russia and the United States.

WAR.WIRE