BENGALURU: Shares of Indian payments firm Paytm tumbled 20% in pre-open trade on Thursday, after a move by the country's financial regulator to halt business at Paytm's payments bank unit sparked fears of hits to the company's profitability and reputation.

Paytm's stock fell to a six-week low of 609 rupees.

The Reserve Bank of India (RBI) on Wednesday ordered Paytm Payments Bank, an associate of Paytm, to stop accepting fresh deposits in its accounts or popular wallets from March, raising worries that the move could erode revenue from the company's main payments business.

(Reporting by Chris Thomas in Bengaluru; Editing by Sonia Cheema)