Fighting between pro-Russian rebels and Ukrainian troops will "most likely affect the MH17 crash site," the Organization for Security and Cooperation in Europe (OSCE) said.
A team of international experts were due to visit the scene where 298 people died today but abandoned their plans for security reasons.
Deputy head of the OSCE mission in Ukraine Alexander Hug said: "We heard indications there's fighting going on.The situation on the ground appears to be unsafe ... we therefore decided to deploy tomorrow morning."
The mother of the three Australian children killed on flight MH17 told a memorial service her "arms would always be reaching for them."
A woman has apparently posted pictures of herself on social media with mascara looted from the Malaysian Airlines flight MH17 crash site.
A large section of plane wreckage and everyday carry-on items like chocolates remain scattered among the wild flowers at the crash site.