Greek stock market authorities have temporarily suspended trading in the country's two biggest banks following press reports that they are in merger talks.

Shortly before the decision, shares in top lender National Bank of Greece and its main domestic rival Eurobank were up 4.5 and 5.5 percent, respectively.

The banks contributed to strong gains being posted by Greek stocks. The bank sector was up nearly 10 percent, while the benchmark general share index rose 5 percent by late afternoon trading.

Greek banks are under pressure to merge after suffering severe damage from the three-year-old financial crisis and a massive writedown in the country's debt earlier this year.

Neither bank would comment on the reported talks.

An NBG official said a statement would be issued later Friday.