Updated

Four days after a senior politician suddenly resigned in Bulgaria, authorities have announced they are investigating him on suspicion of tax fraud and money laundering.

The Sofia prosecutor's office said Thursday that it is focusing on numerous money transfers by Hristo Biserov made between his bank accounts in different European countries.

The prosecution said it has cleared the way for examination of Biserov's tax and banking records and will seek the assistance of authorities in at least two European countries.

Citing unspecified personal reasons, 57-year-old Biserov resigned Sunday as deputy speaker of Parliament and deputy leader of the ethnic Turkish MRF party, a junior coalition partner in the current government.

Biserov could not be reached for comment on Thursday, and Bulgarian national radio said he has left the country.