Fitch Ratings on Oct. 5 lowered the viability rating of İstanbul Takas ve Saklama Bankası AŞ to "b+" from "bb-," citing an increase in the Turkish bank's credit risk exposure, particularly in its treasury activities, following the downgrade of its largest treasury counterparties.

The downgrade follows a similar action on 20 Turkish banks and their subsidiaries.

At the same time, the rating agency affirmed Takasbank's foreign- and local-currency long-term issuer default ratings at BB and BB+, respectively, with negative outlooks, while its national long-term rating was affirmed at AAA(tur), with a stable outlook.

Also affirmed were the bank's B foreign- and local-currency short-term issuer default ratings, 3 support rating, and BB support rating floor.

Fitch noted that the more challenging operating environment, including the ongoing currency and interest rate volatility, would likely put pressure on the bank's overall financial profile, notably its asset quality and capitalization, through its main commercial bank counterparties.