By Krista Hughes

FRANKFURT (Reuters) - The central banks of Britain and Switzerland added extra funds to ease pressure on high interbank lending rates on Thursday, while the European Central Bank said it was ready to step in with extra cash as needed.

The reassuring moves from Europe's three largest central banks helped boost European stocks, following a steady rise in money market lending rates as the end of the quarter nears.

"The ECB continues to closely monitor liquidity conditions and notes tensions in short-term rates as the end-of-quarter approaches, notwithstanding the ample liquidity conditions," the ECB said on its Reuters information page. "The ECB stands ready to provide additional liquidity if needed."

The Bank of England lent 13.62 billion pounds at its regular one-week money market operation, up from 10.93 billion pounds the previous week.

Banks bid for almost three times that much, demonstrating the demand for ready cash.

The Swiss National Bank offered three-month funds at 2.20 percent in a move seen as an attempt to ease money market tensions due to fear of future losses in the banking sector.

German banking giant Deutsche Bank has issued a veiled profit warning due to the credit crisis and Switzerland's UBS and Credit Suisse are expected to announce further losses next week.

Nonetheless, money market rates continued to climb.