MH17 black box
Stills image from a video shows a rescue worker carrying one of MH17's flight data recordersReuters

Rescue workers have recovered flight recorders from the crash site of Malaysia Airlines MH17 believed shot down in eastern Ukraine, but the device is being held by pro-Russian separatists.

On Sunday, a video reportedly taken on Friday was released by Ukraine's security services, showing rescue workers recovering what appeared to be an orange "black box" flight recorder from the wreckage of the stricken aircraft.

The clip was recorded in a wheat field in the village of Hrabove, and shows a Ukraine Emergency Ministry official with a flight-data recorder which was passed to a colleague.

Separatist leader Aleksander Borodai said on Sunday that his men were holding the boxes in Donetsk until experts could confirm they were the plane's recorders.

"They are being held and when they're identified by the International Civil Aviation Organisation we're ready to hand over those objects," Borodai said.

"We were already suspecting that they had them [the black boxes]," Ukrainian vice-prime minister Volodymyr Groysman said. "Over the last few days it has been hard to verify what has been happening with these black boxes."

The news comes after days of international outrage over the ongoing investigation into the crash of the Boeing 777 and the lack of a coherent, independent inquiry.

Investigators, politicians and relatives of the dead worldwide have expressed anger at the Kremlin for not forcing pro-Russia rebels to offer more cooperation, as there has not yet been a detailed examination of the crash site.

The pro-Russian separatists also said they had loaded refrigerated wagons with more than 200 bodies recovered from the crash site. The Associated Press reported that rebels had placed bagged bodies onto trucks and driven them away.

Alexander Pilyushny, an emergency worker combing the crash site for body parts Sunday morning, told reporters he and other workers had no choice but to hand the bodies over to the rebels.

"They are armed and we are not," Pilyushny said. "The militiamen came, put the bodies onto the trucks and took them away."

On Sunday, news agencies reported that no bodies remained at the site.

Al Jazeera journalist Nazanine Moshiri said observers from the European security body, the Organisation for Security and Co-operation in Europe, were present at a nearby railway station where the bodies were being kept.

No international aviation expert or investigator has yet visited the site, as evidence gradually disappears. The OSCE monitors have had to take the word of the local emergency services that 196 bodies have so far been recovered.

Encircled by armed rebels, Alexander Hug, deputy chief of the OSCE mission, said: "We have not been able to count them as that would be too difficult in this situation."

Earlier, the Ukraine government claimed it had reached a preliminary deal with the separatists to take possession of the bodies.

The separatists and Ukraine are accusing each other of firing a surface-to-air missile at the passenger jet as it flew from Amsterdam to Kuala Lumpur on Thursday. Both deny responsibility for the crash.

The aircraft was flying 1,000ft over the no-fly zone over eastern Europe when it was hit, killing 283 passengers and 15 crew members.