The bus driver had apparently ignored the signal of the oncoming train at the barrier-free crossing as the train was approaching at high speed, a local police spokesman told reporters.
The two wounded, including a 14-year-old boy, were taken to a hospital in the city of Iasi in critical condition, the spokesman said.
A three-year-old child was among the fatalities.
There were no casualties among the train passengers. The condition of the minibus driver was not immediately clear after the crash.