Vitaly Nayda, counterintellligence chief for Ukraine's Security Service, told reporters in Kiev that a Russian-made Buk M1 missile system had shot down the Malaysian airline.
He claimed that three Buk surface-to-air antiaircraft missile systems had crossed from Russia to Ukraine prior to the downing of Flight MH17, accompanied by Russian nationals who, he said, were the ones operating the sophisticated weaponry. All three Buk missile systems are no longer in Ukrainian territory, according to Nayda.
Prime Minister Arseniy Yatsenyuk, in an interview with CNN on Saturday, also suggested that whoever operated the missile system received expert training.
"This is not the Russian-led drunk terrorist who pressed the button," he said. "This is someone well-trained. Someone who knows how this machine works. Someone who has experience."