A British vote to leave the European Union would hit large German banks, the head of German financial watchdog Bafin said.
The yen and Swiss franc rose as oil prices slid and bank shares led global equity markets lower, stoking a fresh wave of bids for low-risk assets.
UBS Chairman Axel Weber warned on Tuesday that the beleaguered European banking sector was still facing many challenges.
European markets ended sharply lower on Tuesday as earnings from major banks disappointed, and a sharp decline in mining stocks weighed.
Commerzbank posted a 52 percent drop in first-quarter net profit on Tuesday.
European markets finished mostly in the red on Monday despite a strong recovery in oil prices and mining stocks.
Germany's Commerzbank has named retail banking head Martin Zielke as its next CEO, as the lender prepares to set medium-term targets.
European markets closed mostly lower on Tuesday, as a decline in commodity prices and mixed earnings weighed.
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European markets finished sharply higher on Friday as crude oil prices and mining stocks rebounded.
German lender posts a net profit of $211.4 million in the fourth quarter as it benefited from lower provisions for bad loans.
Deutsche Bank plans to write down the value of Postbank by about a third, ahead of a planned sale of the retail unit, sources said.
Deutsche Bank co-CEO John Cryan said on Tuesday that the bank remained "absolutely rock-solid", given its strong capital and risk position.
Equity markets around the world were met with extreme bearish sentiment on Monday, as global growth worries and the tactics of central banks came under renewed scrutiny.
2016 is proving a difficult year for European banks, as the industry grapples with nonperforming loans, rocky markets, increasing regulation and EM volatility.
Oil prices slumped to a 2003 low below $28 per barrel as the market anticipated a rise in Iranian exports.
Oil prices slumped as China's stock market fall and the prospect of rising Iranian crude exports deepened fears.
China looked set for a soggy start to 2016 after activity in the manufacturing sector contracted for a fifth straight month in December.
China's activity data was stronger than expected in November, with factory output growth picking up to a five-month high.
European equities ended slightly higher on Monday as investors digested more economic news from China and Europe, on top of earnings.