A Malaysian passenger jet which blew up over rebel-held east Ukraine with the loss of all 298 people on board was hit by numerous "high-energy objects", according to a report Tuesday which appears to back up claims it was downed by a missile.

While the preliminary report from Dutch investigators does not point the finger of blame over the July disaster, it could heighten Western pressure against Moscow over its role in the bloody Ukraine conflict.

Malaysia Airlines flight MH17 "broke up in the air probably as the result of structural damage caused by a large number of high-energy objects that penetrated the aircraft from outside," said the Dutch Safety Board report.

International experts have been unable to access the rebel-held crash site northeast of Donetsk because of fighting, and relied on information from the black boxes, Ukrainian officials, as well as pictures and video taken at the scene.

But the findings appear to back up claims that the Boeing 777, which plunged out of the sky on July 17 en route from Amsterdam to Kuala Lumpur, was hit by a missile.

Malaysian Prime Minister Najib Razak said the report "leads to the strong suspicion that a surface-to-air missile brought MH17 down, but further investigative work is needed before we can be certain".

Kiev and the West have accused pro-Russian separatists of shooting it down with a surface-to-air BUK missile supplied by Moscow.

The BUK works by exploding directly outside the target and hitting it with a massive amount of high-velocity shrapnel.

But both Russia -- accused by the West of sending in elite troops and heavy weapons to bolster the pro-Kremlin insurgency -- and the rebels blamed Kiev's forces.

"We simply do not have the military hardware capable of shooting down a Boeing passenger jet such as the Malaysian plane," said Alexander Zakharchenko, prime minister of the self-proclaimed Donetsk People's Republic.

- 'Case still wide open' -

The downing of MH17 was the second tragedy for Malaysia Airlines after the disappearance of flight MH370 in March, and threw the global spotlight back on the uprising in eastern Ukraine.

"We have to guard against drawing premature conclusions," said Dutch Prime Minister Mark Rutte, whose country lost 193 nationals in the tragedy. "The case is still wide open."

The report said the black box recorders had not been tampered with, despite initial concerns over the security of the vast area where the wreckage and the bodies fell.

In its account of the final moments of the doomed plane, it said air traffic controllers had asked it to climb to 33,000 feet (10,000 metres) to avoid three other airliners nearby.

The crew said it was unable to comply, only to ask later for permission to fly higher. It then disappeared, without issuing any distress calls.

"There are no indications that the MH17 crash was caused by a technical fault or by actions of the crew," it said.

The report was issued just a day after the EU adopted new sanctions on Russia over the Ukraine conflict that has killed over 3,000 people including the MH17 victims.

Initially, forensic experts travelled to the crash site near the town of Grabove to collect body parts, but the search has been suspended for a month.

Investigators hope to return to the site if a ceasefire agreed Friday between Kiev and the rebels holds.

Both sides has accused the other of truce violations, with four soldiers and a civilian killed since Friday.

- 'Ready to review sanctions' -

The EU has agreed new sanctions against Moscow -- adding to a series of punitive measures adopted after the downing of MH17 -- but officials said they would hold fresh talks on Wednesday about when to implement them.

"Depending on the situation on the ground, the EU stands ready to review the agreed sanctions in whole or in part," European Council President Herman Van Rompuy said.

The new restrictions would bar Russia's largest state-owned oil and defence firms from using European markets to raise capital and slap more asset freezes and travel bans on officials.

Washington also said it was watching conditions on the ground before deciding on new sanctions. At the moment, the ceasefire was "mostly holding," State Department spokeswoman Marie Harf said.

Russia has warned it would react to sanctions with an "asymmetrical" measure that could see EU airlines banned from flying over its airspace.

However, Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko vowed in a phone call Monday to work to uphold the ceasefire, the first backed by both Kiev and Moscow since the insurgency erupted in April.

Russian Foreign Minister Sergei Lavrov also said Tuesday he hoped talks on the status of the rebel-held areas in Ukraine would start shortly under the terms of the 12-point truce.

Poroshenko has called on the OSCE, the pan-European security body that brokered the deal, to send observers to flashpoint sites.