Tributes have been paid to lost conference delegates aboard Flight MH 17 at the opening session of the 20th International AIDS Conference in Melbourne, Australia, which is scheduled to run from Sunday to Friday.

At least six delegates traveling to the conference, including the former president of the International AIDS Society, were on board Malaysia Airlines Flight MH17, which crashed in Ukraine, killing all 298 passengers.

"It's a senseless loss tous and the world. Our dedication to continue their work fighting HIV/AIDS honors their commitment," IAS President Fran?oise Barre - Sinoussi said at the opening ceremony.

A one-minute silence was held in their honor with 11 former, present and future presidents of the IAS onstage, together with representatives of organizations who lost colleagues.

Lambert Grijns, Dutch ambassador for sexual and reproductive health and rights and HIV/AIDS, read a letter of condolence and support.

"We express the deepest condolences to the families of the victims, who leave a huge void in the conference," he said, adding that five of the six delegates were from the Netherlands.

Condolence books were circulating at the conference and will be available for the duration of the event, said Sian Bowen, senior manager of IAS communications.

On Tuesday, a candlelight vigil will be held at Federation Square in the center of Melbourne to mourn the six MH17 victims and all who have lost their lives to HIV/AIDS, she said.

"The job has not been done yet for a zero AIDS goal," said UNAIDS Executive Director Michel Sidibe, calling for for increasing access to antiretroviral therapy for patients.

In 2013, an additional 2.3 million people gained access to the lifesaving treatments, bringing the global number of people using ART to nearly 13 million by the end of 2013, he said.

Based on the recent scale-up, UNAIDS estimates that as of July 2014 as many as 14 million people had access to ART.