Shares on the Athens Stock Exchange are suffering huge losses of over 22 percent after the market reopened for the first time in more than a month.

The main index plunged early Monday after the country's Capital Market Commission formally approved the reopening of the exchange.

The exchange and Greek banks were closed on June 29, when controls on money withdrawals and transfers were imposed to prevent a collapse in the banking system due to a run on deposits.

Banks have since reopened, while maintaining strict withdrawal limits.

Greece is currently locked in intense negotiations with bailout lenders in an effort to negotiate the terms of a massive new rescue package in the next two weeks.