The operation, involving warship HMS Montrose as part of the Combined Maritime Forces (CMF), lasted almost 10 hours and resulted in the seizure of 663kg of heroin, 87kg of methamphetamine and 291kg of hashish and marijuana.
The Ministry of Defence (MoD) said a Navy team, including Royal Marines, approached a small vessel on two rigid-hulled inflatable boats before securing and searching the vessel.
Illicit substances were then brought back to HMS Montrose for analysis and destroyed.
This is the largest Royal Navy drugs bust since HMS Montrose seized 2.4 tonnes of illicit substances in the Arabian Sea last year, the MoD said.
The Type 23 frigate regularly works alongside international partners which make up the 34-nation coalition CMF, which was led by the Royal New Zealand Navy at the time of the drugs bust.
The leadership role has now passed to the Pakistan Navy.
The CMF is a multinational maritime partnership, which exists to counter illicit non-state actors.
Defence Secretary, Ben Wallace said as a result of the “successful bust” the streets are safer, adding that the operation had “choked off a huge source of finance to international organised crime groups”.
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