Japanese conservatives protested Friday against US congressional demands for a clear apology over wartime military brothels, saying the women were not sex slaves but camp followers.

Lawmakers and academics gave the US embassy in Tokyo a letter saying they were "surprised and shocked" by the pressure for a fresh apology to the "comfort women."

Shoichi Watanabe, history professor emeritus at Tokyo's Sophia University said: "If America keeps saying this is a human rights issue, then what were the indiscriminate bombings on Tokyo and other cities? What were the atomic bombings? Compared with that human rights issue, prostitution in battlefields is only a commercial act."