Romania's largest bank shares tumbled after the competition watchdog imposed a record fine over alleged collusion in setting money-market rates. Banca Transilvania, which received the biggest fine, fell as much as 2.6% while BRD-Groupe Societe Generale SA dropped 3.6%. The fines mark the highest penalties ever issued in Romania for rate manipulation.

The competition authority didn't disclose specific dollar amounts, but the sanctions stem from an investigation into potential coordination among banks in the interbank lending market. This probe examined whether lenders improperly influenced benchmark rates that guide trillions in global transactions. The case aligns with broader European regulatory efforts targeting financial benchmark integrity.

Investors reacted swiftly to the news, with both banks experiencing sharp share price declines. The penalties arrive amid heightened scrutiny of Romanian financial institutions following previous compliance issues. Market participants are now assessing whether additional banks face potential sanctions from the ongoing investigation.

The stock declines underscore mounting pressure on Romanian financial institutions facing evolving compliance standards. With €1.2 billion in combined market capitalization at risk, the case highlights regulatory exposure in emerging European markets.