Ukraine separatist rebels block plane crash observers

A team of international observers said pro-Russian rebels in Ukraine have limited their access to the wreckage of a Malaysia Airlines plane.

An OSCE spokesman said access to the site had been controlled by armed men, with one firing shots into the air.

It is believed flight MH17 crashed after being hit by a surface-to-air missile fired from a rebel-held area in east Ukraine on Thursday.

All 298 people - including 80 children - on board died.

The Boeing 777 was flying from Amsterdam to Kuala Lumpur. It fell between Krasni Luch in Luhansk region and Shakhtarsk in the neighbouring region of Donetsk.

This followed US President Barack Obama claims that evidence so far indicated that the airliner was shot down by a surface-to-air missile from an area in Ukraine controlled by Russian-backed separatists.

Obama said on Friday that it was not the first time the separatists had shot down planes in the region, adding that a "steady flow of support from Russia" had included heavy weapons and anti-aircraft weapons.

He called for an immediate ceasefire to allow for a full investigation into Thursday's air crash.

"This is an outrage of unspeakable proportions," Obama said.

"An Asian airliner was destroyed in European skies filled with citizens from many countries, so there has to be a credible international investigation into what happened."

Officials from the FBI and the National Transportation Safety Board were on their way to Ukraine to help determine what happened, Obama said.

He said that evidence must not be tampered with as a UN-backed investigation went forward.

"We will hold all its members, including Russia, to their word" in allowing access to the crash site, Obama said.

Malaysia Airlines Flight 17 crashed at Grabovo, about 40km from the border with Russia near the regional capital of Donetsk, an area that is a stronghold of rebels who have been fighting Ukrainian government forces.

The debris rested "in a vast area around wheatfields with a circumference of at least 10km", Al Jazeera's Scott Heidler, reporting from the crash site, said.

Leaders of the rebels' self-proclaimed Donetsk People's Republic denied any involvement and said a Ukrainian air force jet had brought down the intercontinental flight.