The bank's shares were suspended just after Milan's FTSE Mib opened, after dropping 2.71 percent.
The bank had said on Sunday it was considering a capital hike after failing a stress test by the European Central Bank, but that state aid was not being considered.
The bank said it is in discussions with authorities over the planned hike and that it is examining the option of covering "the entire capital shortfall through a capital increase".
Other options it is considering include the sale of certain assets to improve its finances, it said.
The bank's directors are due to discuss these plans on Wednesday before announcing its decision on November 10.
Monte dei Paschi de Siena, Italy's third biggest by the number of branches, was among a handful of financial institutions that failed the ECB's audit published last week.
The financial health check, the most comprehensive and most stringent of eurozone banks, is aimed at preventing a repeat of the crisis that nearly led to the euro's collapse.