LONDON/FRANKFURT (Reuters) – Deutsche Bank shares dropped as much as 3.4% in Friday’s premarket trade, after a sharp jump in the cost of insuring against the risk of default late the day before fuelled concerns about the overall stability of Europe’s banks.

Deutsche shares, which have lost a fifth of their value so far this month already, were last indicated up 0.9% in premarket trade on the Lang & Schwartz platform.

They closed 3.2% lower on Thursday, while the bank’s credit default swaps – a form of insurance for bondholders – shot up to 173 basis points from 142 bps the day before, according to data from S&P Market Intelligence on Thursday.

This marks the largest one-day rise in Deutsche’s CDS on record, according to Refinitiv data.

(Reporting by Amanda Cooper; Editing by Dhara Ranasinghe)