ZURICH- The Swiss franc climbed to its highest since July 2015 against a struggling euro on Monday as concerns about the spread of the coronavirus drove investors into safe-haven assets.

The franc, traditionally sought in times of uncertainty, rose to 1.0604 versus the euro, a 4-1/2 year peak and a higher value than it reached after Britain's shock vote to leave the European Union in June 2016.

But Swiss shares tumbled as investors took fright at the virus' spread in neighbouring Italy, with the Swiss Market Index trading 3.4% lower, its biggest one-day loss since August 2016.

Analysts said the franc's surge reflected the currency's role as a safe haven, and could trigger currency interventions by the Swiss National Bank to halt its rise.

The total level of sight deposits rose to 592.26 Swiss billion Swiss francs from 590.13 billion francs, according to data published on Monday, indicating the SNB has been active in foreign exchange markets. 

Sight deposits, money parked by commercial banks with the SNB overnight, is often seen as a proxy for central bank interventions.

The SNB declined to comment, although Chairman Thomas Jordan said earlier this month that he thought the coronavirus outbreak had increased investor appetite for the franc. 

Fears of a pandemic are growing after sharp rises in new cases reported in Iran, Italy and South Korea although China has relaxed restrictions on movements in several places, including Beijing, as new infection rates there eased. 

"There is no doubt the Swiss franc is coming under heavy pressure from investors in a risk-off environment due to the coronavirus, that's why the currency has risen," said Karsten Junius, an economist at J.Safra Sarasin.

"If the franc continues to rise the SNB will come more significantly into the market. If the franc breaks through to 1.05 something, that is the level I think it will defend."

(Reporting by John Revill; Editing by Catherine Evans) ((John.Revill@thomsonreuters.com; +41 58306 7022; Reuters Messaging: john.revill.thomsonreuters.com@reuters.net))