TOKYO (AFP) - Japan's hawkish defence minister prayed on Thursday (Dec 29) at a controversial war shrine in Tokyo the day after accompanying Prime Minister Shinzo Abe on a symbolic visit of reconciliation to Pearl Harbor, drawing swift condemnation from neighbour South Korea.

Yasukuni Shrine honours millions of mostly Japanese war dead, but is contentious for also enshrining senior military and political figures convicted of war crimes by an international tribunal.

The indigenous Shinto religious shrine has for decades been a flashpoint for criticism from countries such as South Korea and China, which suffered under Japan's colonialism and military aggression in the first half of the 20th century.

Tomomi Inada's visit to the shrine was her first since taking the key defence portfolio in August, though she has frequently gone in the past.

"By taking a future-oriented stance, I offered my prayers to build peace for Japan and the world," she told reporters.

She noted that Barack Obama - "the president of a country that dropped atomic bombs" - had gone to Hiroshima earlier this year, while Abe "voiced words to console the spirits of the dead" at Pearl Harbor, though she did not mention that Japan attacked it.

Inada made the pilgrimage the day after, in Japan time, Abe and Obama's joint visit to the site of the Japanese military's December 7, 1941 attack on the navy base in Hawaii that drew the US into World War II.

Inada is a close confidante of Abe and holds staunchly nationalist and revisionist views.

Abe, who was playing golf, said he had "no comment" on her visit, Jiji Press reported.

South Korea was quick to criticise Inada and summoned a senior official from the Japanese embassy in Seoul to protest.

"Our government cannot but deplore" the visit, foreign ministry spokesman Cho June Hyuck said in a statement, while in separate comments the defence ministry expressed "grave concern and regret".

Inada's move was an attempt to appease the government's conservative base after Abe's conciliatory gesture to the US, analysts said.

"As Ms Inada was present at Prime Minister Abe's visit to Hawaii, she wiped off some - if not all - of her reputation as a revisionist," said Tetsuro Kato, emeritus professor of Japanese politics at Hitotsubashi University.

"But she also had to address frustrations from right-wingers among her supporters," he told AFP.

Koichi Nakano, professor of politics at Sophia University and a vocal Abe critic, said Inada's visit to Yasukuni was not a rogue act.

"Yasukuni is not a normal Shinto shrine," he said. "Naturally, she went with Mr Abe's blessing." Inada's conservatism is well known.

She wrote in 2011 that Japan - the only country in the world to suffer atomic bomb attacks - should consider acquiring nuclear weapons.

In August after becoming defence minister she said that Japan "should not consider arming itself with nuclear weapons at this moment".

In 2014, she and another conservative lawmaker were seen in separate photographs standing next to the leader of a Japanese neo-Nazi party, though spokesmen for both denied any political affiliation.

Inada argued Thursday that paying respect to war dead should be universally accepted, echoing the argument repeated by Japanese lawmakers who frequently visit Yasukuni.

Conservative lawmakers visit the shrine on the anniversary marking Japan's surrender in World War II as well as other occasions, and Masahiro Imamura, another cabinet minister, went on Wednesday.

That was just hours after Abe and Obama paid homage to the more than 2,400 Americans killed in Japan's surprise assault against the Pacific Fleet and issued declarations about the power of reconciliation and warned against fomenting conflict.

The prime minister's Pearl Harbor visit followed Obama's May journey to Hiroshima, the scene of the world's first atomic attack days in August 1945.

Abe has himself avoided Yasukuni after going there three years ago to commemorate his first anniversary as prime minister.

That sparked fury in Beijing and Seoul and earned a diplomatic rebuke from close ally the United States, which said it was "disappointed" by the action.

Japanese conservatives have called on him to resume visits.