The nation’s top four lenders – Piraeus Bank, National Bank, Alpha Bank and Eurobank – fell the most, all down 30%, the maximum allowed. Banks make up about a fifth of the index.
The bourse was shut just before Athens imposed capital controls at the height of the debt crisis.
It had fallen behind by 22.87% just minutes after opening for trade.
The Athex recovered slightly in morning trading, but was still down more than 18% in midday trading.
In accordance with conditions laid down by the government and the European Central Bank, local investors are not allowed to buy shares with money from their bank accounts, only with cash kept in safe deposit boxes or at home.
Meanwhile, data released on Monday showed that Greek manufacturing activity plunged in July to its lowest level on record as a three-week bank shutdown caused new orders to dive and created serious supply problems.
