Australian and New Zealand joint forces have seized 915 kilograms of heroin, valued in excess of $274 million, in a counter-narcotics operation in the Western Indian Ocean.

A Royal New Zealand Air Force P-3K2 aircraft detected a suspicious vessel on January 23 and a crew from Royal Australian Navy frigate HMAS Warramunga boarded the boat on January 24.

Over the past two months Warramunga's crew has taken part in operations resulting in the seizure of more than 11.5 tonnes of hashish and over 1 tonne of heroin, valued in excess of $900 million.

Commander of Australian Defence Force personnel in the Middle East, Rear Admiral Jaimie Hatcher, RAN, said the latest operation highlighted the significant contribution both Australia and New Zealand make to maritime security in the region.

"Warramunga has now interdicted six vessels carrying illegal narcotics since November," Rear Admiral Hatcher said.

"This operation highlights the important role played by partner nations, as part of the Combined Maritime Forces, in increasing maritime security in the Middle East and Western Indian Ocean."

Commanding Officer of HMAS Warramunga, Commander Dugald Clelland, said the operation was a team effort between close partners.

The illegal drugs were transferred to Warramunga for disposal at sea.