A black Monday for Greece's stock market. Its benchmark Athens Stock Exchange Index ended the day 16% lower after it re-opened for the first time in five weeks.

The bourse, which was shut at the height of the country's debt crisis, had plunged 22.87% immediately after opening, although it recovered slightly in morning trade.

Monday's slump was the biggest since at least 1987.

The biggest losers were the banks, which make up about a fifth of the index. The Piraeus, Alpha Bank, National Bank of Greece, and Eurobank all shed 30%, the daily limit allowed by the index.

The banks, which had been suffering from massive cash withdrawals for months, shut down June 29 to prevent money rushing out of the financial system, and then re-opened three weeks later.

The extended closure left many Greek factories short of cash to sustain operations, causing manufacturing to fall to its record low in July. Manufacturing accounts for a tenth of Greece's economy, which, according to the European Commission, may shrink 4% this year.

As in the re-opening of the banks, trading at the stock market was hampered by capital controls. Locals could buy shares, bonds, derivatives, and warrants with cash on hand and earnings from the future sale of shares or investment account balances. They could also use funds from abroad but not from their bank accounts. There were no restrictions for foreign investors.

“It’s a total disaster, it’s like hell here,” Stavros Kallinos, head asset manager at Guardian Trust, told Bloomberg from Athens. “You can’t have a market working properly with capital controls.”

Although short-selling is banned, the restrictions practically make it easier for investors to sell, which may undermine confidence in the market mechanism and integrity, the Association of the Members of the Athens Exchanges told Bloomberg.

Traders expect the situation to get worse in the coming days. And investors could be in for huge losses. This after Greece agreed with European creditors last month to place much of the burden of rescuing banks on investors.

Such agreement was part of new bailout terms that Greece accepted in exchange for emergency financing to avoid defaulting on its debts.

Greece is now looking forward to the bailout worth $96 billion from European partners. $26.7 billion of the package will be used in repairing Greek banks' finances.

Currently, the banks stay afloat with emergency cash from the European Central Bank. By far, Greece has already received 7.16 billion euros ($7.86 billion) in an emergency loan from Europe. It must make a payment to the ECB by August 20 to remain in the euro zone.

The bailout deal is still being finalized by the Greek government with its European creditors.