An international AIDS conference opened in Australia on Sunday with a tribute to several delegates who were killed en route to the gathering when their plane was shot down over Ukraine.

Officials at the opening ceremony for the 20th International AIDS Conference in Melbourne held a moment of silence for the six AIDS researchers and activists killed aboard Malaysia Airlines Flight 17. All 298 people on board the plane died when it was shot down by a surface-to-air missile Thursday as it flew over rebel-held eastern Ukraine.

Among the passengers was prominent Dutch researcher Joep Lange, former president of the International AIDS Society, and World Health Organization spokesman Glenn Thomas, based in Geneva.

Around 12,000 scientists and activists from 200 countries are attending the conference to discuss the latest developments in HIV and AIDS research.

The current president of the International AIDS Society, Nobel Prize laureate Françoise Barré-Sinoussi, dedicated the conference to those who were killed, and a candlelight vigil will be held Tuesday to commemorate their lives. Condolence books were also being passed around for attendees to sign.

"It's a really important time for what we think everyone needs, which is a space to grieve and to respect the six members of our community that died on MH17," conference co-chair and AIDS researcher Sharon Lewin said.