A leading human rights watchdog is calling on the Indian government to repeal an old law that bans homosexual sex. Criticism of India's homosexual laws has been triggered by the recent arrest of a group of gay men.

The calls for scrapping the 19th century law follow the arrest this week of four people on charges of homosexuality in the northern Indian state of Uttar Pradesh. The men have also been accused of running an online gay club.

Homosexuality is illegal in India, and can be punished by up to 10 years in prison.

In a letter to the prime minister, the U.S.-based organization Human Rights Watch says these "colonial-era" laws encourage the spread of HIV by preventing people from coming forward for testing, information and services.

The United Nations program on HIV/AIDS has similar concerns. The India coordinator for UNAIDS, Denis Broun, says treating homosexuals as criminals increases the stigma and discrimination they face and hinders the fight against AIDS.

"It creates a climate of fear and distrust among this community of men who have sex with men," he explained. "They may be illegal in India at present but they exist, and among them the spread of HIV/AIDS is faster than in the general population. So it essential that these people can have a climate of trust where they will be able to assemble, where they will be able to share information."

In the city of Lucknow, where the four men were arrested, a gay rights organization working among the city's homosexual community accuses the government of double standards. The head of Naz Foundation International, Arif Jafar, says the government asks NGOs to work with high-risk groups in order to tackle the country's growing AIDS crisis, but then makes it difficult to reach out to these people.

Jafar says the recent arrests have sparked tremendous fear among the city's homosexual community.

"They are all scared," he said. "There have been tremendous number of calls. They are all scared what should they do now, should they run away, should they go underground."

In India's conservative society, homosexuality is frowned upon, but the gay community is slowly trying to lift the veil of secrecy surrounding it. In New Delhi on Thursday, about two dozen gay activists held a rare protest demanding the release of the four arrested men and carrying banners proclaiming "My sexuality, My Right", and "Queer and Proud."

Indian gay activists have also pressed for the law banning homosexual sex to be scrapped.

Broun of UNAIDS urges a change in the law.

"This law dates back to the puritan era of colonization," he said. "I think it is time for India to review its criminal law, taking into consideration evolution of behaviors and populations in the 21st century and take an Indian criminal law rather than the old English one."

However, the Indian government has argued that scrapping the law could result in an increase in homosexuality.