A vehicle drove onto the runway of the main British base in Afghanistan then burst into flames at around the same time the US Defence Secretary arrived there today.
Leon Panetta arrived to meet with troops, commanders and Afghan government officials just days after a US soldier went on a deadly shooting spree.
Around the same time, a vehicle got onto the runway at the base and caught fire, sources said.
The driver, a local male civilian employed at the base, is being treated at Camp Bastion's hospital for his injuries, a spokeswoman at the base said.
One British serviceman suffered minor injures in an earlier incident which may be linked to the same vehicle.
The spokeswoman added: "Procedures were put in place to account for the whereabouts of all military and civilian personnel and, to achieve this, movement within Camp Bastion was restricted."
Ministry of Defence police patrolled roads inside the base today in the wake of the incident.
US defence secretary Leon Panetta arrived at Bastion on Wednesday
Flights and movements in and out were restricted throughout the afternoon while it was investigated and were lifted later on.
Bastion is home to a large contingent of US troops as well as UK forces.
The incident comes as relations between Isaf forces and Afghan locals are increasingly tense.
At the weekend 16 Afghan civilians, including several children, were shot dead by a US soldier.
Last month there was anger after US troops burned Korans on an American base.
Panetta's two-day visit is scheduled to include meetings with President Hamid Karzai, Afghan defence officials and provincial leaders, as well as routine discussions with his commanders on the ground.
His aircraft is said to have not been at any risk from the incident.
Asked about the incident at a White House press conference with US President Barack Obama, Prime Minister David Cameron said it was not yet clear exactly what had happened.
"It is very early details still coming through. Obviously we will want to examine and investigate exactly what has happened before making clear anything about it," he said.
"But the security of our people, of our troops - the security of both our nation's forces - is absolutely the priority.
"If there are things that need to be done in the coming hours and days to keep them safer, be in no doubt we will do them."
Canadian soldiers attend a graduation ceremony of Afghan soldiers in Kabul