A team of international police officers that had been due to visit the site of the Malaysia Airlines plane disaster in eastern Ukraine has cancelled the trip after receiving reports of fighting in the area.
Alexander Hug, the deputy head of a monitoring team from the Organisation for Security and Cooperation in Europe, said it would be too dangerous for the unarmed mission to travel to the area from its current location in the rebel-held city of Donetsk.
It was not immediately clear where clashes had broken out.
Malaysia Airlines Flight 17 was shot down with a surface-to-air missile over a part of eastern Ukraine controlled by pro-Russian separatists last week, killing all 298 people on board.
US and Ukrainian officials say it was shot down by a missile from rebel territory, most likely by mistake.