A coalition of human-rights and AIDS activists on Monday demanded the release of two AIDS experts detained in Iran.

The men, brothers Arash and Kamiar Alaei, were detained by Iranian security forces in late June, without being charged. Their whereabouts remain unknown, Human Rights Watch (HRW) said on the sidelines of the XVII International AIDS Conference currently underway in Mexico City.

'The local Iranian press quoted deputy prosecutor of Tehran, Hassan Hadad, saying that the brothers have been accused of trying to overthrow the government,' Joe Amon, HRW's HIV/AIDS programme director, told Deutsche Presse-Agentur dpa by telephone.

'Their families have had no news of them. We don't know where they're being held, and they haven't been given any access to legal counsel.'

Physicians for Human Rights (PHR) has launched a website, IranFreeTheDocs.org, which is collecting signatures on a petition urging the Iranian government to respect the doctors' basic human rights.

On June 22, security forces detained Arash, holding him overnight at an unknown location. The next morning, they took him home, where they arrested his brother, according to an HRW statement.

The doctors were scheduled to present a case study at the Mexico conference on injection drug use and AIDS in Iran.

The Alaei brothers are pioneering AIDS researchers in Iran, and made the country an unlikely leader in the prevention and treatment of HIV and AIDS.

They played a large role in the creation of Iran's HIV/AIDS prison programme, said to be one of the best in the region, if not the world. Condoms and syringes are handed out in prisons, making Iran one of only a handful of countries doing so.

'Iran's HIV/AIDS programme has been acclaimed internationally for seriously addressing the AIDS epidemic,' said Amon.

To fight AIDS effectively, the government has realized that it must engage in global efforts to combat the disease, work with civil society and confront taboo issues, including sex and drugs. The detention without charges of the Alaei brothers has a chilling effect on all of those efforts.'

Kamiar, a doctoral candidate at the SUNY Albany School of Public Health, was to return to his programme in September. Arash is a former director of the International Education and Research Cooperation of the Iranian National Research Institute of Tuberculosis and Lung Disease.

Since 1986, the Alaei brothers have worked to integrate prevention and care of HIV/AIDS, sexually transmitted infections and drug- related harm reduction into Iran's national health care system.

They have worked closely with government and religious leaders to ensure support for education campaigns on HIV transmission, including those targeting youth.

'We urge the government of the Islamic Republic of Iran to release them immediately so that they can continue their important medical and public work for the betterment of the people of Iran and the world,' said PHR chief executive Frank Donaghue.

HRW's Amon said: 'Iran cannot be considered to be making progress (on AIDS) if it is blatantly violating the human rights of two of its most valuable activists in this area.'