Two suspects of Vietnamese origin, one a German federal employee, are being questioned by the German authorities over the abduction last month of the former Vietnamese official, Trinh Xuan Thang.
A Vietnamese citizen, identified only as Long NH, was handed over by the Czech authorities on Wednesday following an extradition request.
German prosecutors suspect that he hired the car used in the abduction of Thanh and a female companion in Berlin on July 23.
He is accused of espionage and being an accessory to unlawful detention.
The other is named by the German authorities as Ho NT, a long time employee of Germany’s Federal Office for Migration and Refugees, who has been honoured by the Communist authorities in Hanoi for his propaganda work.
He was suspended from his duties at the migration bureau in the days after the kidnapping on suspicion he could have provided information to the suspected kidnappers.
Mr Thanh had been due to present his case for asylum in Germany at the migration office in Berlin on July 24, the day after he was grabbed in the Tiergarten district and bundled into the car by seven suspected agents.
He appeared in Hanoi more than a week later to say that he had decided to turn himself in to face charges of misappropriating $150m during his time as head of the construction arm of the Vietnamese state oil company.
Mr Thanh had previously alleged that the charges against him were politically motivated and that he had no chance of receiving a fair trial in a country where the courts are subservient to the will of the Communist party.
Suspicion fell on Mr Ho when it was revealed that he had been moonlighting as a correspondent for Vietnamese state media publications.
He was lauded for by the Communist authorities two years ago for “special services to propaganda” for an article on the crisis in western democracy.
He is reported to have written in the aftermath of Thanh’s disappearance that the incident would be quickly forgotten because, he asserted, the current foreign minister, Sigmar Gabriel, was a “lame-duck”.