BRATISLAVA, Slovakia — Slovakia's prime minister says his government will do all it can to investigate his country's possible involvement in a kidnapping case that has strained relations between Germany and Vietnam.

Germany accused Vietnamese intelligence agents of kidnapping a Vietnamese businessman from a Berlin street in July 2017. Trinh Xuan Thanh, the former chairman of PetroVietnam's construction arm, was seeking asylum in Germany.

Slovak Prime Minister Peter Pellegrini spoke of an investigation on Monday after Slovak and German media reports suggested Slovakia allowed visiting Vietnamese officials to borrow a government plane to fly from Bratislava to Moscow with Thanh onboard.

After he reappeared in Vietnam, Thanh was given two life sentences for embezzlement. Vietnam claims that Thanh returned voluntarily.

Slovak authorities have denied wrongdoing.