KUALA LUMPUR (REUTERS) - Malaysian Prime Minister Najib Razak demanded swift justice for those responsible if a Malaysian airliner that came down in Ukraine was found to have been shot down.

Mr Najib, reading out a statement at a news conference on Friday, said Malaysia had not been able to verify what caused the plane to crash while on a flight from Amsterdam to the Malaysian capital, Kuala Lumpur, but it had not made a distress call.

But he had agreed in talks with US President Barack Obama that investigators must get full access to the site of the crash.

"The Ukrainian authorities believe that the plane was shot down," Mr Najib said in the statement.

"At this stage, however, Malaysia is unable to verify the cause of this tragedy. But we must, and we will, find out precisely what happened to this flight. No stone will be left unturned."

"If it transpires that the plane was indeed shot down, we insist that the perpetrators must swiftly be brought to justice."

He said also that Malaysia was sending a special flight to Kiev with a disaster assistance and rescue team.