An Australian warship patrolling in the Middle East has seized a haul of 581kg of heroin with an estimated street value of more than half a billion euro, a naval official said this morning.

Commander of Australia's Joint Task Force 633, Brigadier Nagy Sorial, said it was the second largest haul ever by the Combined Maritime Forces.

CMF is a 30-nation naval partnership which patrols 2.5 million square miles of international waters.

"The weekend's find made Australia's maritime contribution to CMF one of the world's most effective current heroin interdiction forces," Brig Sorial said in a statement.

HMAS Newcastle intercepted a stateless dhow off the east African coast where her boarding party uncovered the drugs, the statement added, without saying which country's shoreline it was closest to.

The guided missile frigate enforces maritime security with a focus on terrorist activity and piracy in the Middle East and Indian Ocean regions, as part of the US-led Combined Task Force, which operates under the CMF.