A number of people heading to an international Aids conference were reportedly on board the Malaysia Airlines flight that crashed in eastern Ukraine.
Several researchers were heading to the AIDS2014 conference in Melbourne, Australia.
"The International AIDS Society (IAS) today 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," a statement on the organisation's website 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."
Thousands of online users have taken to social media to call for the victims of the Malaysian airliner crash to be returned to loved ones.
United States intelligence officials admitted that they do not know who fired the surface-to-air missile that downed flight MH17.
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