The Ukrainian Ministry of Internal Affairs (MVS) has released a video which it claims shows the Buk missile defence system reportedly used to shoot down Malaysian Airlines flight MH17 over eastern Ukraine crossing the border back into Russia.
The footage, which has not been independently verified, recorded at 4.40am local time on Friday, shows the Buk system on a board a truck, missing one missile.
Earlier, the Ukrainian security service the SBU released what it alleges is a transcript of an intercepted conversation in which a Russian army officer and militant discuss the delivery of the Buk into Ukraine in the early hours of Thursday morning, only hours before the plane was shot down.
"Yes, yes, yes," says the rebel. "Buk, Buk," records the transcript.
"Is it on a tractor?" replies the officer.
"Yes . . . We need to unload it somewhere, in order to hide," the rebel replies.
The SA-11 missiles, known in Russian as Buks, are packed with 121-pound warheads and can reach a height of 40,000 feet.
US officials said that they believed an SA-11 was used to down the plane.
MH17 was cruising at an altitude of 33,000 when it was shot down.
The Russian Defence Ministry has denied that the Buk system crossed into the country from Russia.
A ministry official also denied that any other military equipment had crossed the border from Russia.
"Such crossings cannot be performed in secrecy", the official told Russia Today.
Russian Foreign Minister Sergey Lavrov dismissed claims of Russian involvement from the Ukrainians.
"Regarding those claims from Kiev that we allegedly did it ourselves: I have not heard a truthful statement from Kiev for months," he said.
Ukrainian Security Service chief Valentin Nalivaychenko claimed that two Russian citizens who acted as 'spotters' for Buk missile systems, helping militants to operate the sophisticated equipment, had been detained by Ukrainian security services.
The defence official denied that spotters were used for Buk missile systems.
"We should clarify that such specialists as spotters are used only for those weapons systems, which are aimed at engaging ground-based targets," he said.
Previously, the Russian Defence Ministry claimed that a Ukrainian Buk was operational in the Donetsk region, where the plane was shot down with the loss of almost 300 lives.