Russian President Vladimir Putin said Ukraine bore responsibility for the downing of a passenger plane in the country's east, saying it would not have happened if Kiev had not resumed a military campaign against separatists.

"This tragedy would not have happened, if there had been peace on that land, or in any case if military operations in southeastern Ukraine had not been renewed," he said in televised comments.

"And without doubt the government of the territory on which it happened bears responsibility for this frightening tragedy," he said, adding that he had urged the Russian authorities to do everything possible to help with the investigation into the incident.

"We will do everything that we can so that an objective pictured of what happened can be achieved," Putin said. "This is a completely unacceptable thing."