China's government on Thursday called on Japan to "break clean with militarism" after Tokyo confirmed that Prime Minister Shinzo Abe sent a note earlier this year to a ceremony honoring more than a thousand World War II-era war criminals praising their contributions.

Abe sent the message to an annual ceremony April 29 at the Koyasan Buddhist temple in central Japan in his capacity as head of the ruling party, not as prime minister, Chief Cabinet Secretary Yoshihide Suga told reporters Wednesday.

"I humbly express my deepest sympathy for the martyrs ... who sacrificed their souls to become the foundation of peace and prosperity in Japan today," Abe wrote in his note, a copy of which was obtained by The Associated Press through the ceremony organizers' office. "I hope for eternal peace and pledge to work toward a harmonious coexistence of mankind in the future."

Many Asian countries that suffered from Japanese militarism in the first half of the 20th century see honoring war criminals as a lack of remorse by Tokyo for wartime aggression. The revelation of Abe's note could especially worsen Japan's ties with China and South Korea, which have repeatedly criticized Abe's views on wartime history, widely seen as revisionist.

China's Foreign Ministry on Thursday said Japan should reflect on its invasion and make a "clean break with militarism" to rebuild relations with Asian neighbors.

"We urge Japan to adhere to its commitment to reflect on the invasion and take solid action to win the trust of Asian neighbors and international community," spokesman Qin Gang said in the statement.

Tokyo's relations with Beijing and Seoul have been badly strained since Abe prayed last December at Tokyo's Yasukuni Shrine, which honors 2.5 million Japanese war dead, including 14 executed "Class-A" war criminals.

More than a year and a half since taking office, Abe has not been able to hold bilateral meetings with the leaders of the two countries.

Abe's message was read aloud to about 220 people who attended the April ceremony, according to Midori Nakatsuji at the organizers' office. She said Abe sent a similar message to last year's memorial service.

The ceremony was held in front of a stone monument that honors about 1,180 Japanese war criminals, including wartime Prime Minister Hideki Tojo and the 13 other executed officials.

The "Class A" criminals were convicted of crimes against peace and humanity by the International Military Tribunal for the Far East, held in Tokyo by the allied forces after the war. Suga acknowledged that Japan has accepted the tribunal's decisions, laid out in the San Francisco Peace Treaty, as a condition for the country's return to the international community.

Abe, however, has said that those convicted by the tribunal are not considered war criminals under domestic law.

Ceremony organizers said on their website that the tribunal was the victors' "retaliation" against the losers, and that those who were executed were "wrongfully convicted" by the allies and their honor should be restored.