The euro/franc exchange rate fell to 0.9910 in Asia overnight, as investors sought refuge in the Swiss currency. The valuation is the highest level for the franc since January 2015 when the Swiss central bank scrapped its peg to the euro.

"The Swiss franc is currently sought after as a refuge currency, along with the US dollar and the yen," the central bank said in a statement.

"The Swiss franc continues to be highly valued," it added. "The SNB remains prepared to intervene in the foreign exchange market if necessary."

The verbal intervention is an unusual move by the central bank, which last gave a separate statement indicating its concerns about the franc's appreciation after Britain voted to leave the European Union in 2016.

"While the SNB has been rather relaxed about the appreciation of the Swiss franc in the last months ... a drop below parity could change its attitude because parity is also a psychologically important threshold," UBS economist Alessandro Bee said.

The SNB said the increased valuation of the franc, which is a danger for Switzerland's export-dominated economy, also recognized the inflation differentials between Switzerland and other countries.

Consumer price inflation in Switzerland rose to a higher-than-expected 2.2% in February, the highest level since 2008, but well below the 5.8% level in the neighboring eurozone, Switzerland's biggest export market.

The SNB on Monday said it looked at the overall currency situation rather than individual currency pairs.

Sight deposit data, a proxy for the SNB's foreign currency purchases, showed a rise of just 500 million francs last week, indicating a small amount of intervention. Obviously, the bank is hoping with the announcement of its measures to achieve some outflow on the foreign exchange market.

"I expect the SNB to fight this appreciation only moderately – because it cannot change the environment for investors that just seek safety," J. Safra Sarasin economist Karsten Junius said.

Russia's invasion of Ukraine, which it calls a "special operation" has introduced uncertainties as the global economy looks to move towards monetary policy normalization, SNB Governing Board Member Andrea Maechler said in an interview published on Saturday.

Her comments pointed out that the crisis had delayed the SNB's plans to retreat from the negative interest rates and foreign exchange purchases, which had been the basis of its expansive approach.

The Swiss central bank gives its next monetary policy update on March 24. Obviously, if cash inflows continue, the institution will be forced to lower the franc exchange rate, otherwise exports and imports will cost the Swiss too much.