A large weapons cache has been uncovered and seized by HMAS Darwin, following the boarding of a fishing vessel during their deployment in the Middle East region.

Darwin intercepted the vessel approximately 313 kilometres off the coast of Oman to conduct a flag verification boarding.

The team are operating under the Australian-led Combined Task Force 150 (CTF150), which is responsible for counter-terrorism operations within the region.

After assessing the vessel to be stateless, a number of weapons, including 1989 AK-47 assault rifles, 100 rocket propelled grenade launchers, 49 PKM general-purpose machine guns, 39 PKM spare barrels and 20 60mm mortar tubes were seized from the vessel that was headed towards the Somalia coast.

The weapons were seized under United Nations sanctions, which authorise interdiction on the high seas of illicit weapons destined for Somalia.

Chief of Joint Operations Command Vice-Admiral David Johnston said the seizure on Darwin's first patrol of such a large haul of illicit weapons is highly significant.

HMAS Darwin is conducting Maritime Security Operations under the authority of Combined Task Force 150 in the Indian Ocean and Arabian Gulf. ( Supplied: Department of Defence/ABIS Sarah Ebsworth )

"Australia worked as part of the multi-national Combined Maritime Forces (CMF) to discover and seize these illegal weapons," Vice-Admiral Johnston said.

"One of the key reasons HMAS Darwin is deployed to the region is to contribute to global security and counter international terrorism.

"Darwin's successful boarding and subsequent seizure of the weapons concealed under fishing nets highlights the need to remain vigilant in the region."

CMF is a multinational effort to prevent terrorism, piracy and drug smuggling, encourage regional cooperation and promote a secure maritime environment in the Middle East and off the north-east coast of Africa.

This is Darwin's seventh deployment to the MER and the 62nd rotation of a RAN vessel in the region since 1990.