A Canadian warship has made a major drug bust at sea.

The Department of National Defence says HMCS Toronto has seized around 500 kilograms of heroin from a boat in the Indian Ocean.

The drugs were found after a naval boarding party searched the vessel as part of a security operation this past Friday.

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HMCS Toronto's commanding officer says it is one of the largest heroin seizures in a maritime environment.

Commander David Patchell says the bust doesn't just keep drugs off the street but also affects the finances of international terrorist organizations.

The HMCS Toronto is currently part of a international naval task force patrolling the Arabian Sea and Indian Ocean.