SYDNEY, July 18 -- Some of the world's top AIDS experts, bound for an international conference in Melbourne, Australia, were among those killed in Malaysian Airlines MH17 crash, the International AIDS Society (IAS) announced on Friday.

In a statement on its website, IAS said the loss of so many lives was a deep tragedy.

"IAS expresses its sincere sadness at receiving news that a number of colleagues and friends en route to attend the 20th International AIDS Conference taking place in Melbourne, Australia, were on board the Malaysian Airlines MH17 flight that has crashed over Ukraine earlier today," the statement said.

"At this incredibly sad and sensitive time the IAS stands with our international family and sends condolences to the loved ones of those who have been lost to this tragedy."

It is believed the former president of the International AIDS Society, Joep Lange, was among those killed. He had been involved in HIV treatment and research for more than 30 years, working for the World Health Organization.

He was also the founder of the not-for-profit PharmAccess Foundation which aims to provide and improve access to health care in Africa.

Former U.S. president Bill Clinton and singer and activist Sir Bob Geldof are among the high-profile speakers attending AIDS 2014, the 20th International AIDS Conference, which will start on Sunday.