Warships belonging to the US, Turkey, France and Portugal, backed by helicopters and warplanes, identified, isolated and seized a civilian vessel carrying an imaginary cargo that could be used in the making of a nuclear weapon.
"This is the first time Turkey has hosted such an exercise deploying naval, land and air forces," Air Commodore Tuncay Erilmez told reporters attending the Anatolia Sun 2006 manoeuvres in the east Mediterranean.
"We never want to deal with such a situation but this exercise will help ensure we are ready if there ever is one," he said, noting that WMD proliferation has become a global worry.
Turkish officials said the exercise was not aimed against anybody, though some media have speculated that it is meant to discourage Iran, which is currently locked in a diplomatic battle with the West over its nuclear programme.
The US and its allies suspect Iran of trying to build a nuclear bomb, though Tehran insists its programme is aimed at producing peaceful atomic energy. Iran has a land border with Turkey.
During the exercise, the allies try to make contact with the civilian vessel without success. A corpse is then thrown into the sea. A suspicious helicopter draws near to the boat but is scared off by a Turkish naval helicopter.
Sailors finally manage to board the vessel, discover its dangerous cargo and take it ashore where teams of experts in special masks and costumes collect it and take it away for proper study and decontamination.
"The aim of the Anatolia Sun 2006 exercise is to test and develop information and intelligence exchange, consultation and political decision-making processes and operational mechanisms at both national and international levels," Turkey's foreign ministry said in a statement.
Turkish commandos taking part
in the Mediterranean Sea drill
Security experts from Nato and from more than 30 countries observed the exercise, conducted near Turkey's popular holiday resort of Antalya.
"This is a very well organised exercise and we have learned a lot," said one Greek observer, requesting anonymity.
"Greece is also thinking of organising such an exercise involving WMD in the near future. Turkey is a very important actor in the region."
On Tuesday, Turkish and Greek warplanes collided over the Aegean, not far to the west of Friday's exercise, sparking mutual recriminations. The Greek pilot died in the accident.
Swift communication between the two countries' military and civilian authorities helped defuse the situation.