(CNN) A Slovak investigative journalist and his fiancée were found shot dead Monday, the first time a reporter has been murdered in the country, according to police.

Jan Kuciak, 27, reported on tax evasion and fraud among Slovak businesses, including people connected to the Slovak governing party, Smer.

The journalist for news website Aktuality.sk and his fiancée Martina Kušnírová were found with bullet wounds to the chest and head respectively, said the International Press Institute (IPI).

The couple was shot at Kuciak's apartment in Velka Maca, western Slovakia, some time between Thursday and Sunday, according to police.

Policemen stand guard outside Jan Kuciak's apartment Monday.

The head of the Slovak Police, Tibor Gaspar, said it was "likely" the murder was connected to Kuciak's work as an investigative journalist.