Britain's Royal Navy sailors have completed a five-month drug-smuggling operation in the Gulf region and Indian Ocean during which narcotics worth 515 million U.S. dollars were captured, the Ministry of Defense (MOD) announced Sunday.

The MOD said since April, British, French, U.S. and Australian warships in a Combined Task Force have taken part in Operation Southern Surge to counter narcotics trafficking.

The Royal Navy warship, HMS Monmouth, was involved in eight drugs operations seizing 1.75 tonnes of narcotics, it said.

"The multinational coalition is focused on deterring and denying maritime terrorist activity in the region, which includes some of the world's most vital trade routes such as the Suez Canal and Bab Al Mandeb Strait," said an MOD spokesman.

Britain's Defense Secretary Sir Michael Fallon said: "The money made from these nefarious criminal activities fund the terrorists who threaten us at home and abroad. As we leave the EU, we will continue to work alongside our allies to tackle smuggling in the region and maintain the free flow of shipping."

Navies from the Combined Maritime Forces, a coalition of 31 nations, take turns to lead the task force either from a command ship or the headquarters in Bahrain.

The Franco-British team has been directing operations since April after taking over from the Canadian Navy, and has now passed on command to the Pakistan Navy.