France, Belgium and Luxembourg are to bail out Dexia, following fears the troubled bank could go bankrupt.
The Belgian government will buy the bank's division in Belgium for 4 billion euros ($US5.4 billion).
And Luxembourg Finance Minister Luc Frieden said a Qatari investment group was ready to buy the bank's Luxembourg unit.
Trading in Dexia's shares, which had been suspended, resumed on Monday afternoon. The BBC reports the price immediately fell 36% before recovering slightly.
Dexia also secured state guarantees of up to 90 billion euros to secure borrowing over the next 10 years. Belgium will provide 60.5% of these guarantees, France 36.5% and Luxembourg 3%.
Deutsche Welle Radio reports Dexia is Belgium's second largest bank.
It is a largely retail operation with 6000 employees, handling deposits totalling 80 billion euros for four million customers.
Dexia has a global credit risk exposure of around $US700 billion.
Dexia previously had to be bailed out in 2008, with the Belgian, French and Luxembourg governments putting in 6.4 billion euros to keep it afloat.