International monitors trying to investigate the crash site of Malaysian Airlines plane MH17 that was 'shot down' over the Ukraine on Thursday are being blocked from the scene by "drunk gunmen", according to an NBC news report.

On Friday, a group from the Organisation for Security and Cooperation in Europe (OSCE) tried to gain access to the crash site, to scour fields where the bulk of debris and human remains are lying, but a gang of rebels brandishing guns reportedly stopped them from reaching the scene to carry out their investigations.

OSCE spokesman Michael Bociurkiv told NBC News that warning shots were fired by the rebel unit commander and that the rebels acted in an "impolite and unprofessional" manner when the organisation tried to reach the crash site.

"We had expected unfettered access, that's the way we work," Michael Bociurkiw told a news conference. "Unfortunately the task was made very difficult. Upon arrival at the site... we encountered armed personnel who acted in a very impolite and unprofessional manner. Some of them even looked slightly intoxicated."

The monitors reportedly remained at the site for an hour and a quarter before leaving, frustrated by the way they'd been treated and the lack of access.

According to Bociurkiw, the bodies from the wreckage of Malaysia Airlines MH17 that they could see looked like they had not been touched, adding that their personal possessions had been arranged in piles, as if "for show".

According to a BBC report, the Ukraine has accused pro-Russian rebels of trying to destroy evidence of international crimes at the crash site of a Malaysia Airlines plane.

The site where the Malaysian Airlines plane crashed has been the location of intense fighting between pro-Russian separatists and the Ukrainian military.

The OSCE are attempting to gain access to the crash site again on Saturday. A BBC report has said that the rebels are now allowing access "on foot" around the site but that European Monitors would not be allowed direct access to the wreckage.

Downing Street has said six investigators from the UK Air Accidents Investigation Branch will be joining other international experts arriving in Kiev to assist in the investigation into the causes of the crash, which killed 298 people, including nearly 200 Dutch passengers, 10 Britons and 80 children.