Investors dumped Credit Suisse shares and bonds on Monday after rival UBS agreed over the weekend to take over the 167-year-old bank for a fraction of its market value and with huge support from the Swiss government.

Credit Suisse shares fell nearly 62 percent to about 0.61 Swiss francs ($0.6578) in pre-market trading in Switzerland, while the value of its Additional Tier 1 (AT1) bonds - a contingent convertible bond considered the riskiest type of debt a bank can use - came after the bank said 16 billion Swiss francs worth of debt would be written down to zero. It fell to a low of one dollar and one cent.

Credit Suisse announced on Sunday that the debt had been written down on the orders of Swiss regulators as part of rescue measures to merge with UBS. That angered bondholders.

"The next few hours of trading will give us a better idea of whether the crisis has been contained," said Ipek Ozkardeskaya, senior analyst at Swissotel Bank.

"In theory, there is no reason for Credit Suisse's crisis to expand, because what triggered the last earthquake at Credit Suisse was a crisis of confidence - this has nothing to do with UBS. "Ubs is a bank that has not been affected by the turmoil and, in addition, has ample liquidity and guarantees from the Swiss National Bank and the government."

Under the plan hatched by Swiss regulators on Sunday, UBS would pay 3 billion Swiss francs ($3.23 billion) for Credit Suisse and take losses of up to $5.4 billion.

At Friday's close, Credit Suisse's total market value was $8 billion. Just six months ago, it was worth $13 billion.

Ubs's shares, meanwhile, fell nearly 5 percent to around 15.81 francs in premarket trading.