Deutsche Bank, Germany's biggest lender, said Monday it has bought back $740 million (680 million euros) of its own dollar-denominated bonds as part of a bid to assuage concerns about the solidity of its finances, but the amount was smaller than expected.

Earlier this month, the bank announced plans to repurchase up to $2.0 billion of dollar-denominated securities, as well as 3.0 billion euros of euro-denominated securities.

The moves were part of a multiple offensive to allay fears which also saw its new chief executive John Cryan take the unusual step of issuing a public statement and writing to Deutsche Bank's employees to say that the group "remains absolutely rock-solid, given our strong capital and risk position."

In a short statement on Monday, Deutsche Bank said that investors had tendered a total $740 million of dollar-denominated bonds for it to buy back.

It already bought back 1.27 billion euros of euro-denominated bonds last week.

"The relatively low investor participation in the public tender offers for both the euro-denominated and US dollar-denominated securities tendered reflects improved market sentiment and an investor preference to retain exposure to Deutsche Bank," the statement said.

The entire European banking sector lost about a fifth of its market capitalisation in January, dragged down by weakness in the eurozone economy and challenges facing banks from ultra-low interest rates and regulatory pressures.

But Deutsche Bank has taken a bigger battering because it is also entangled in a web of legal woes. Its share price has plunged by a third since the beginning of the year.  

The bank faces a quagmire of as many as 6,000 different litigation cases, the provisions for which helped push it to a record loss of 6.8 billion euros last year.  

It was fined last May a record $2.5 billion for its involvement in rigging interest rates, and has faced probes by Swiss authorities for suspected price fixing on the precious metals market.

US investigators have also looked into its Moscow branch on suspicion of possible involvement in money laundering.