Swiss bank UBS AG posted a fourth-quarter loss on charges stemming from alleged manipulation of interest rates, but the Zurich-based bank's loss was less than expected, and it also reported a 6 percent increase in operating income for the three months.

The bank, Switzerland's largest, said on Tuesday that it lost 1.84 billion francs ($2.08 billion) in the last three months of 2012 compared compared with a profit of 323 million francs in year-earlier period. Wall Street analysts polled by Bloomberg News expected a loss of 2.16 billion francs.

The loss stemmed largely from a fine the bank paid to settle charges of participating in manipulating the London Interbank Offered Rate, or Libor, a global lending rate benchmark. The loss also reflected a charge for laying off about 10,000 employees.

The increase in third-quarter operating income reflects interest income and revenue from trading and fees.

UBS said it lost 2.51 billion francs last year compared with a profit of 4.14 billion francs in 2011.