A Dutch-led international team of criminal investigators on Wednesday will release initial findings into the downing of Malaysia Airlines flight MH17 amid growing frustration among relatives over the probe's pace.

The preliminary findings are expected to shed light on the exact type of BUK missile which struck the Boeing 777 passenger liner mid-air on July 17, 2014, killing all 298 people on board including 196 Dutch citizens.

It is also expected to show exactly where the Russian-made missile was fired from in war-torn eastern Ukraine, where Kiev has been battling pro-Russian separatists since April 2014.

But the Dutch prosecution has already cautioned that it will not be naming any suspects at the briefing, taking place in the central town of Nieuwegein, near Utrecht.

Investigators will meet relatives of the victims first to give them the results, after which a press conference is planned for 1100 GMT.

"Apart from wanting to know exactly what weapon was used and where it was fired from, we also want an answer as to where we go from here," said Evert van Zijtveld, chairman of the foundation that supports families of MH17 victims.

"We want to see the perpetrators caught and put on trial," he told AFP.

Van Zijtveld voiced frustration at the progress of the probe, saying "in any case, it doesn't seem that this problem can be solved by politicians."

"We hope the perpetrators will be caught soon. The last thing we want is to sit with a situation similar to Lockerbie," he said, referring to the bombing of a Pan Am jet over the town of Lockerbie 26 years ago in which 270 people were killed.

Libyan Abdelbaset Ali Mohmet al-Megrahi was only found guilty 12 years later in 2001 -- the only person ever convicted of the crime. He maintained his innocence until his death in 2012.

Russia this week again sought to deflect the blame for the MH17 disaster, accusing Kiev, in a move some Dutch newspapers said aimed to pre-empt Wednesday's report.

Ukraine and the West insist pro-Russian rebels blew the jet out of the sky with a Russian-made missile system likely supplied by Moscow.

- Russian denials -
A separate international civil inquiry, headed by the Dutch safety board, concluded last October that a BUK missile fired from a zone held by pro-Russian separatists brought down the aircraft.

But it stopped short of saying who was responsible.

Russia and the rebels have denied any role in downing the plane, releasing a series of sometimes contradictory claims that critics say are intended to muddy the issue.

At a specially-arranged briefing on Monday, Russia's defence ministry released what it said were radar images showing that no missile fired from rebel-held territory in the east could have hit the plane.

Russia said the fact the Ukraine had not yet released radar information suggested the location from which the missile was launched -- if it was a BUK -- was in territory controlled by the Ukrainian armed forces.