March 20 (Reuters) - Prices on Additional Tier 1 (AT1) bonds from European banks fell sharply on Monday after Credit Suisse's wipeout of such debt raised concerns about the broader sector.

Credit Suisse on Sunday said 16 billion Swiss francs worth of its AT1 debt will be written down to zero on the orders of the Swiss regulator as part of its rescue merger with UBS , in a decision that surprised bondholders and raised questions about the safety of investing in such debt issued by other banks.

Bid prices on AT1 bonds from banks including Deutsche Bank , HSBC, UBS and BNP Paribas dropped 10-12 cents on Monday, data from Tradeweb showed.

AT1 bonds - also known as "contingent convertibles" or "CoCo" bonds, are deeply subordinated and convert into equity or are written off if a bank’s capital level falls below a certain threshold, depending on the deal terms. (Reporting by Yoruk Bahceli, editing by Karin Strohecker)