Dutch prosecutors say they have identified many "persons of interest" in their probe into the shooting down of flight MH17 over Ukraine, but no definite suspects.

"We have a large group of people that we're at this stage branding 'persons of interest' in whom we have an above average interest," Dutch chief prosecutor Fred Westerbeke told a press briefing in Rotterdam on Tuesday.

"But we've not yet taken the formal step of making them suspects," he told journalists, almost a year after the Malaysia Airlines flight was downed over war-torn Ukraine, killing all 298 on board, the majority of them Dutch.

The Netherlands has been tasked with leading the investigation into the cause of the disaster and identifying the victims of the July 17, 2014 crash.

It is also in charge of the criminal prosecution of those responsible.

Westerbeke said although "great steps" were being made in the criminal probe to find those responsible, a dossier to take to trial would not be ready "at least before the end of the year."

Kiev and the West claim that the plane was shot down by pro-Russian separatists using a BUK surface-to-air missile supplied by Moscow.

Russia has denied the charges, pointing the finger instead at Kiev.

Shortly after the crash, the UN Security Council adopted Resolution 2166 which demanded that those responsible "be held to account and that all states cooperate fully with efforts to establish accountability."

The Netherlands has floated the idea of a UN-backed tribunal, an idea to which veto-wielding Security Council member Russia is opposed.

The Boeing 777 was flying from Amsterdam to Kuala Lumpur when it was shot down.

In an initial report published last year, the Dutch Safety Board said the plane had been hit by numerous "high-energy objects".

A final report is due later this year.