"Libor is a mythical number, " said Meyrick Chapman, a debt-market analyst at Swiss bank UBS. The rate had meant little to the market before the start of the global credit crunch in September 2007, but it has become an important indicator of how corporate loans are priced.

FORBES: Market Scan

The Swiss National Bank surprised markets by cutting its key interest rate target by 0.25 percentage points, citing growing economic uncertainty amid sharp plunges in global equity markets and a reduced risk of inflation.

CNN: European markets routed

Some suggest the Swiss ought to announce a peg to the euro or engineer a negative nominal interest rate.

ECONOMIST: How to live with an overvalued currency

Denmark cut its deposit rate below zero in July last year, and in December, the Swiss bank Credit Suisse imposed negative rates on bank deposits to tame demand for the Swiss franc.

BBC: Negative interest rates idea floated by Bank's Paul Tucker

Swiss bank UBS is reportedly near a settlement with American and British regulators over interest-rate rigging.

FORBES: Libor Scandal Extended To UBS: Bank Reportedly Near $450M Settlement With Regulators

The Swiss bank is said to be nearing a settlement with American and British regulators over interest-rate rigging.

FORBES: Why UBS Is Better Off Than Barclays In Libor Rigging Case

Since then, Swiss bank UBS and the Royal Bank of Scotland have been fined hundreds of millions of pounds for rigging the rate, which is used to set a range of financial deals.

BBC: Libor fines to fund armed forces charities, says Osborne