By Jonathan Davies

Shares in Greece fell nearly 23% this morning as stock markets opened for the first time in five weeks.

The Athex stock market opened 22.87% as trading resumed. Greece's four biggest banks - Piraeus Bank, National Bank, Alpha Bank, and Eurobank - all fell by around 30%, with Piraeus the worst affected.

Banks are crucial to shares in Greece, making up around 20% of the Athex and around a quarter of all Greek stocks.

The index did recover slightly, but still remained 18% lower by midday (local time).