One of Europe's biggest banks has gone on the offensive to stamp out talk that its finances may be fragile.

At the end of a turbulent week for its shares, Deutsche Bank (DB) said it planned to buy back more than $5 billion worth of its debt.

The bank said Friday its "strong liquidity position allows it to repurchase these securities without any corresponding change to its 2016 funding plan."

Deutsche shares shot up nearly 10% Friday.

Companies buy back bonds from the secondary market if they can repay investors less money than waiting for the securities to mature.

"By repurchasing this debt below its issue price, the bank realizes a profit," finance chief Marcus Schenck said in a statement.

Deutsche was forced to reassure investors about its financial strength after its shares crashed Monday, and fell again on Tuesday. They rebounded on Wednesday after the buyback plan was first reported by the Financial Times.

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Co-CEO John Cryan wrote a letter to employees on Tuesday describing the bank as "absolutely rock solid." The letter was subsequently published by the bank.

It also issued a statement Monday to say it had more than enough cash to service its debt through 2017.

Schenck said Friday the bank had around 215 billion euros ($241 billion) in reserves at the end of 2015, equivalent to 120% of its short-term funding needs.

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There are other reasons companies buy back debt. They have to insure against defaulting on their bonds and those costs rise if markets get jittery. The fewer bonds on the market, the lower the insurance costs.

European bank shares have been slammed this year by fears about slowing global growth, the oil price collapse, negative interest rates -- which trash their margins -- and the cost of regulation and litigation.