Some Monte dei Paschi customers have been pulling savings out of the Italian bank, its chief executive said today.
The Italian bank is facing a crisis over a mountain of bad loans that has halved its market value this year.
CEO Fabrizio Viola did not say how much money savers had withdrawn, or when the outflow began.
But he did say that the fall in deposits was "limited" and that the bank could cope with it as he sought to reassure customers and investors.
Italian bank shares have lost 20% so far this year as investors, already rattled about global economic growth, have sold out of a sector with low profitability and about €200 billion of loans that are unlikely to be repaid.
Monte Paschi - Italy's third-biggest bank - has lost the most ground as it is perceived to be the most vulnerable.
It has the highest level of bad loans as a proportion of assets and was the worst performer in a 2014 health check of euro zone lenders.
The Tuscan-based bank's stock, which had sunk 15% on Monday and 14.4% yesterday, was suspended from trading several times after falling 18.2% today.
"Of course clients turning to our local branches are worried about what they read," Viola said in a statement.
"At present the size of the funding lost due to clients who decided to move part of their savings elsewhere is limited and anyway below levels seen during the previous crisis the bank faced in February 2013 which was overcome brilliantly," he added.
The 2013 crisis he was referring to was when the world's oldest bank, already badly weakened by the euro zone debt crisis, was hit by a scandal about loss-making derivatives trades.
Italian lenders' huge pile of soured loans is tying up capital and holding back fresh credit that could support a fragile economic recovery in the country.
A boost to bank stocks from merger speculation following an overhaul of cooperative lenders last year has fizzled out as a deal has yet to materialise.
Monte Paschi was told by the European Central Bank to seek a buyer after the 2014 health check. It appointed UBS and Citi as advisers more than a year ago but has so far failed to find one.
Viola said the plunge in Monte Paschi shares was not areflection of the bank's fundamentals, which he said had improved in the last quarter of 2015.
He said revenues rose both compared with the third quarter and from a year earlier while costs were cut, adding that liquidity levels at the end of 2015 were at their highest in four years and the bank's capital base was adequate.
The bank's CEO also said that he was confident the bank would weather the current crisis and that the recent fall in the stock did not appear to be linked to sales of big stakes.
