The drill, code named ``Blue Odyssey,'' was the sixth such security trial to train for mass casualties from chemical, biological or nuclear attacks. The exercise is also expected to include mock hostage scenarios at sea, authorities said. Media coverage was banned.
More than 1,000 police, coast guard and fire department officers joined the exercises at Athens' main port of Piraeus and along the rocky coastal area of Palea Fokia, about 30 miles southeast of the capital.
Representatives of a seven-nation advisory group, which includes the United States, Britain and Israel, were expected to observe the maneuvers. Russian officials were also on hand helping Greece with security planning for the Aug. 13-29 Olympics.
Greece has budgeted a record sum of more than $750 million to safeguard the games. Authorities plan to deploy more than 50,000 security personnel, including 16,000 soldiers, during the Olympics.