A United States marine has died after being injured in routine training just outside of Darwin.

Lance Corporal Hans Sandoval-Pereyra, 21, died on Tuesday after succumbing to injuries received during a tactical vehicle accident on Saturday, the Marine Expeditionary Force said in a statement.

He was conducting routine training at the Mount Bundey training area, about 120 kilometres south-east of Darwin, when he was injured.

He was initially treated at the scene before being transported by helicopter to Royal Darwin Hospital where he died.

The cause of the accident is under investigation.

However, US military and veteran organisation Military.com reported that he was a passenger in a Humvee that ran off the road and rolled.

One other marine received minor injuries in the accident, but has since been released from hospital.

"We are saddened by the loss of Lance Corporal Sandoval-Pereyra," said Colonel Russ Boyce, Commanding Officer for Marine Rotational Force — Darwin (MRF-D).

"He was a beloved member of our community and our deepest sympathies go out to his family and friends.

"We are extremely grateful to our Australian partners for their valiant efforts to save this young marine's life."

Lance Corporal Sandoval-Pereyra's death is the second in May for the Marine Corps, the US Naval Institute reported.

A light armoured vehicle rolled over on May 9 at Camp Pendleton in California, injuring six and killing one.

In April, a Marine Raider was killed when the MRZR vehicle he was driving rolled over.

US Marines and Australian troops train together in the Northern Territory during May 2019. ( Facebook: Marine Rotational Force Darwin )

Lance-Corporal Sandoval-Pereyra was from Fairfax, Virginia, and was an expeditionary airfield systems technician assigned to the Aviation Combat Element for the marines in the Top End.

Before being deployed to Australia, he was assigned to Marine Wing Support Detachment 24, Marine Aircraft Group 24, based at Marine Corps Base Hawaii, Kaneohe Bay.

His decorations include America's National Defence Service Medal and the Global War on Terrorism Service Medal.

His death was not the first at Mount Bundey.

Earlier this month, the Commonwealth Department of Prosecutions laid charges against the Australian Defence Department over the death of a young Australian soldier during a live-firing exercise at the training area in 2017.

It's also not the first death of a marine in Australia — three marines were killed in a US military aircraft crash off the coast of Queensland in August 2017.