International prosecutors investigating the downing of flight MH17 over eastern Ukraine in 2014 say the Buk missile that hit the plane was transported from Russia.

All 298 people on board the Boeing 777 died when it broke apart in midair flying from Amsterdam to Kuala Lumpur.

Robby Oehler, whose niece was killed in the crash, told the BBC that prosecutors told relatives they will investigate about 100 people over the incident.

"They told us how the Buk was transported [and] how they came to that evidence from phone taps, photo, film material, video," he said.

He said prosecutors said the missile was fired from territory controlled by pro-Russian rebels.

The Dutch-led Joint Investigation Team (JIT) consists of prosecutors from the Netherlands, Australia, Belgium, Malaysia and Ukraine.

An inquiry by the Dutch Safety Board last year found that a Russian-made Buk missile hit the plane but did not say where it was fired from.

The JIT investigation's findings are meant to prepare the ground for a criminal trial.