Warsaw police commander Jarosław Szymczyk received the gift during a recent visit to Ukraine.
Poland's police chief Jarosław Szymczyk has been hospitalised with minor injuries after a gift he received from Ukraine exploded.
The blast occurred on Wednesday morning at the police headquarters in Warsaw, the Polish Interior Ministry said.
A civilian employee also suffered minor injuries but did not require medical treatment. The building also suffered damage.
The ministry did not confirm what object had exploded but stated that Szymczyk had received it as a present during his recent visit to Ukraine.
Szymczyk had met with leaders of the Ukrainian Police and Emergency Situations Service on Sunday and Monday, the ministry added.
Polish authorities have asked Ukraine to provide "relevant explanations". The regional prosecutor's office in Warsaw has launched an investigation.