MELBOURNE, Australia -- An international AIDS conference has opened in Australia with a tribute to several delegates who were killed en route to the gathering when their Malaysia Airlines plane was shot down.

Officials at the opening ceremony for the 20th International AIDS Conference in Melbourne held a moment of silence Sunday for the six HIV/AIDS researchers and activists killed aboard Malaysia Airlines Flight 17. All 298 people on board the plane were killed when it crashed Thursday in eastern Ukraine.

Among the conference delegates killed was Joep Lange, former president of the International AIDS Society and a prominent AIDS researcher from the Netherlands.

The conference has drawn around 12,000 experts in HIV and AIDS from 200 countries.