Cocaine with a street value of up to $300 million has been seized from a yacht in the Solomon Islands after an international drug investigation involving Australian, Solomon Islands and US DEA officers.

Two men have been charged in Sydney after the 500-kilo haul, destined for Australia, was discovered concealed in the hull of a Belgian-registered, 13-metre yacht moored in Honiara.

The Australian Federal Police allege the large vessel travelled from South America across the Pacific Ocean, and the syndicate behind the cocaine haul was arranging another “handover” at sea before venturing to Sydney.

Australian Federal Police Detective Superintendent Ben McQuillan described the operation as “unprecedented” with international collaboration “pivotal” in helping Australian authorities lay these charges.

“This is an unprecedented operation between Australian and Solomon Islands authorities, illustrating what can be achieved when our partners collaborate to stop large-scale drug importations before they have a chance to reach Australian communities,” Detective Superintendent McQuillan said.

The investigation ended on Thursday after simultaneous police raids in Sydney and Honiara. Photo: Australian Federal Police

The two Australian citizens faced Sydney’s Central Local Court on Friday.

A 41-year-old man from Wahroonga has been charged with knowingly dealing in money or other property which is an instrument of crime valued at greater than $50,000, and conspiracy to import commercial quantity of border-controlled drugs, which carries a maximum penalty of life behind bars.

“He’s a senior figure within a group of which he is one of, if not, the head,” Detective Superintendent McQuillan told reporters in Sydney on Saturday.

“In relation to the large-scale importation of narcotics, this person has been looked at for quite some time.”

A 39-year-old man from Bonnyrigg Heights is also facing one count of dealing with an instrument of crime.

“We’re still yet to completely weigh the seizure and to analyse it but I think I’d be comfortable in saying probably a street value of between $200 to 300 million would be a reasonable estimate,” Detective Superindenent McQuillan said.

It is the largest major organised crime probe undertaken by the AFP with the Royal Solomon Islands Police Force.

“It’s certainly a seizure which … the magnitude has not been seen previously in that part of the world,” he said.

He said upwards of eight tonnes of cocaine has now been seized in similar circumstances since February 2016, “most of which, if not all of which, we believe was destined for Australia”.

Australian Border Force Regional Investigations NSW Superintendent Garry Low said investigators had once again been able to contribute to efforts to keep dangerous substances off Australian streets.

“We know the demand for cocaine in Australia is increasing and tackling this issue requires a multi-layered approach through disruptions offshore, detections at the border and targeting the facilitators here in Australia,” Superintendent Low said.