Canada's armed forces said the helicopter had been involved in an accident after taking off from the Canadian frigate Fredericton on Wednesday.

"Debris has been found in Italy's zone of control and intervention" in the Ionian Sea, the Greek military officer told AFP, specifying the wreckage belonged to the Canadian helicopter.

Six crew were aboard the helicopter when it disappeared, the officer said on condition of anonymity.

Greek public television reported that a body had been found amid the wreckage in international waters off the Greek island of Kefalonia.

But the military officer did not immediately confirm a body had been found, saying only that Greece has sent a marine helicopter to take part in the rescue operation.

Greek public television ERT said Italian and NATO vessels were also taking part in the search while Turkish said one of its frigates was also involved.

The Canadian Armed Forces has not confirmed any debris has been found.

It said on Twitter that it contacted the family members of those who were on board the missing CH-148 Cyclone helicopter.

The aircraft was "involved in an accident in the Mediterranean Sea," it said, but gave no other details.

CAF had issued a statement earlier saying it had lost contact with the helicopter deployed on board HMCS Fredericton which was participating in NATO exercises off the coast of Greece.

- Allies join search -

"Search and rescue efforts are currently under way," it added.

CAF has not said so far how many personnel were on board.

Initial reports said the helicopter had been over international waters 50 nautical miles off Kefalonia.

Italian, Greek and Turkish frigates were taking part in the exercises along with the Canadians.

Juanita Chang, spokeswoman for Supreme Headquarters Allied Powers Europe (SHAPE), which plans and carries out all NATO operations, confirmed Wednesday that a helicopter had gone missing.

"I confirm there has been an incident involving a helicopter from a ship under NATO command," she said.

"There is currently a search and rescue operation being conducted and national notifications taking place."