Bulgaria's central bank warned of an attempt to destabilise the country on Friday following an apparently coordinated campaign to spread rumours that some of its banks were in financial trouble, triggering public panic.
"In recent days there has been an attempt to destabilise the state through an organised attack against Bulgarian banks without any reason," a central bank statement said.
In the latest incident, messages sent to the public by an unknown source via mobile phones and the Internet said the First Investment Bank (FIB), the country's third largest, was in dire financial straits.
An interior ministry official said two other unnamed banks were targeted in a similar way.
The rumours provoked scenes of near panic in the capital, with lines quickly forming outside bank branches as clients rushed to withdraw their money.
The same thing happened a week ago to the Corporate Commercial Bank (CCB), the fourth biggest Bulgarian bank, forcing it to suspend payments and place itself under the central bank's protection.
Doubts about the CCB, majority-owned by a controversial businessman, were raised after police raided its headquarters and questioned 12 top managers.
Bulgarians have bitter memories of a grave financial crisis in 1996-97, when 14 banks, many of which owned shares in the others, went under in a little over one year.
FIB initially fought back on Friday, saying in a statement that it would honour all requests for withdrawals even if it had to stay open later than normal.
But in the early afternoon it suspended such operations owing to "technical problems" after paying out 800 million leva (400 million euros, $545 million).
It then pledged to "serve clients normally starting Monday."
Central bank governor Ivan Iskrov insisted on Friday that that the banking system was "functioning without problem" in a statement.
Bulgarian banks collectively hold the equivalent of 20.6 million euros ($28 million) in deposits from individuals, and 11.8 billion euros ($16.1 billion) from companies, he said.
Interior Minister Tsvetlin Yovtchev denounced "an attack" on the FIB, while another ministry official said that two other unnamed banks had suffered similar attacks.
The total represents 81 percent of the national gross domestic product in 2013.