A highly organized gang of five, thought to be responsible for a string of bank heists in the capital over the past two years, is believed to be behind yesterday’s attack on a bank in Gyzi, central Athens, police said. The gunmen managed to escape with an undisclosed sum from the National Bank of Greece branch at 34 Gyzi Street after a brief exchange of fire with members of a passing police patrol. There were no casualties. Police are particularly interested in the fact that the gang, suspected of having robbed another four Athens banks since November 2002, seems to have added an automatic weapon to its arsenal of handguns. Officers will try to establish whether the gun is the same as that taken from police guard Haralambos Amanatidis, who was murdered at his post outside the British military attache’s residence on New Year’s Eve. A terrorist link is suspected in the murder.