The Athens General Index (GR:GD) -6.84% led declines among European bourses on Monday and plunged 6.8% to 566.79 as National Bank of Greece SA (GR:ETE) -13.61% tanked 13.6%.

Casino and betting firm OPAP SA (GR:OPAP) -6.39% gave up 6.4%, while Hellenic Petroleum SA (GR:ELPE) -7.63% tumbled 7.6%.

Across Europe, most country-specific indexes posted steep declines as confidence faded that the leaders at the European Union summit later in the week will take the appropriate measures to contain the region's debt crisis.

Greece's newly elected Prime Minister Antonis Samaras and Finance Minister Vassilis Rapanos won't be able to attend the summit, however, due to health issues.