Five former high school teachers filed a damages lawsuit Tuesday claiming they were denied part-time teaching jobs after retirement because they refused to stand and sing the national anthem during a school ceremony.

In the complaint lodged with the Tokyo District Court, the teachers said they were reprimanded for disobeying the principal's order to sing "Kimigayo" during a graduation ceremony in March 2004.

The teachers are demanding 28 million yen from the Tokyo Metropolitan Government, which runs the school, claiming its decision not to re-employ them on a contractual basis because of the reprimand violates the Constitution.

According to the complaint, the teachers applied for contract jobs because they had reached mandatory retirement age and had to leave the school by the end of March but still wanted to work. But the metropolitan board of education denied them jobs without citing specific reasons.

The teachers said in the complaint that the principal's order amounted to a violation of the Constitution.

"It was also unconstitutional that the board of education did not rehire them due to conditions for re-employment not being met, because the teachers failed to obey the order," the teachers said in a statement.

Akishi Miyasaka, 60, one of the plaintiffs, said, "We decided to take legal action because there could be more people who are denied teaching jobs for refusing to stand when the national anthem is sung."

The metropolitan government cannot comment on the case because it has not yet reviewed the complaint, an official said.

"Kimigayo," unofficially translated in English as "His Majesty's Reign," was defined under law as the national anthem in 1999, but its status remains a sensitive issue due to its symbolic links to the Imperial system and Japan's militarist past.