Britain’s Stephen “Luke” Atkinson, aged 57, and Australian Trent Lee, 40, were working on behalf of non-governmental organisation Norwegian People’s Aid (NPA).

They were killed in the blast in the Solomon Islands’ capital Honiara on the island of Guadalcanal.

The South Pacific nation was a key battleground and its islands, including Guadalcanal, are littered with remnants from land and sea clashes between Allied and Japanese forces.

NPA deputy secretary general Per Nergaard called the blast, which occurred in the residential Tasahe area of the nation’s capital Honiara on Sunday (September 20), a "tragic accident".

"So far, we know that there has been an explosion with fatal consequences," a statement on the NPA website said.

"Our main priority now is to offer assistance to relatives and colleagues, and to clarify what has happened."

The NPA is assisting local authorities in the Solomon Islands to develop a centralised database mapping UXO – unexploded bombs - dating back to the Second World War.

While the cause is not yet known by police, Insp Tunuki said preliminary investigations indicated there were "several items of UXO at the residence and they may have been conducting some UXO work".

Earlier this year, Ken Gross Smith, manager of the Solomon Islands 2023 facilities, told the Australian Broadcasting Corporation (ABC) that warships fired in the direction of the King George VI School field in east Honiara, where the athletics stadium and multipurpose hall for the Pacific Games are scheduled to be built.

He revealed that students had been playing on the field for decades without realising the danger beneath their feet, as the unexploded ordnance could be triggered if disturbed or handled incorrectly.

“This used to be one of the battlefields [and] it was a heavy fighting area,” he told ABC.

“This in fact used to be an airstrip.

“I understand that when the shell hits the ground it bends and comes up a bit, so any unexploded ones would still be under there.”

Any unexploded ammunition found is collected by the police bomb squad and taken away to be destroyed.

A total of 15 new facilities, including a stadium, aquatic centre and a futsal complex, are set to be constructed for the Pacific Games, most of them in east Honiara and mostly bankrolled by China.

The Solomon Islands Government is hoping the massive infrastructure work from the sporting event will give the local economy a much-needed boost.

The total cost of the Games is estimated to be around SBD$2 billion (£192 million/$246 million/€211 million).