Mutterings about Swedbank first began circulating online in Latvia around two weeks ago after authorities took over local bank Krajbanka.

Among the claims made on social networking sites were that ATMs in Sweden had been shut-down, that the bank's Estonian operations had been killed off and its Latvian CEO had been arrested.

Speculation intensified over the weekend and worried customers began lining up at ATMs to withdraw their cash, emptying many machines. Swedbank estimates that around 15 million lat was withdrawn over the weekend, seven times as much as normal, says the Wall Street Journal.

In a statement, the bank insists that all of the rumours are unfounded and says it is cooperating with authorities in Latvia and Sweden to stop them and "calm down the situation".