Swiss banking group Credit Suisse has unveiled plans to buy back nearly $6bn of debt raised from the Qatar Investment Authority and Saudi Arabia’s Olayan family during the financial crisis.

The bank will repurchase three convertible bonds, also known as CoCos, which were issued at high interest rates to enable the bank meet Swiss “too big to fail” rules.

The bonds in question are CHF2.5bn of 9% notes, $1.72bn of 9.5% notes, as well as $1.72bn of 9.5% notes.

These bonds have the capability to convert into equity if a bank’s core capital ratio falls below a certain level.

The move forms part of the bank’s strategy to reduce funding costs by $900m. Last month, the bank issued a $2bn tier one capital instrument to redeem the debt.

It also priced a CHF300m tier 1 capital instrument this month, which is scheduled to settle on 4 September 2018.

“This is a key step forward in reducing Credit Suisse’s funding costs, as we continue to reshape our balance sheet and optimise our capital structure. It is another milestone in the bank’s three-year restructuring programme, which is due to be completed at the end of 2018,” a bank spokesman said.

The earliest date for redeeming the bonds has been set at 23 October 2018.