At least six delegates heading for Melbourne to join an international AIDS conference were killed in the crash of Malaysian flight MH17, the meeting organizer said on Saturday.

"The extent of our loss is hard to comprehend or express," Francoise Barr-Sinoussi, president of the International AIDS Society (IAS), said in a statement.

"We grieve alongside all of those throughout the world who have lost friends and family in this senseless tragedy," said the renowned researcher.

There were speculations by the Australian media saying that as many as 108 medical researchers, scientists and activists died in the crash on their way enroute from Amsterdam for Melbourne via Kuala Lumpur.

But officials of the IAS denied this number, saying, "there could be a little bit more than six."

The confirmed deceased include former president of IAS Joep Lange, World Health Organization official Glenn Thomas, Director of AIDS Action Europe Lucie van Mens, AIDS Action Europe member Maria Adriana de Schutter, Pim de Kuijer from STOP AIDS NOW and Jacqueline van Tongeren from Amsterdam Institute for Global Health and Development.

According to Owen Ryan, Executive Director of the IAS, those delegates were attending the conference "because of their dedication to bringing an end to AIDS".

"We will honor their commitment and keep them in our hearts as we begin our program on Sunday," he added.

The AIDS 2014 conference is scheduled to begin on Sunday and finish on 25th of July. According to the organizers, former U.S. president Bill Clinton and singer and activist Sir Bob Geldof are among the high-profile speakers.