US Defence Secretary Leon Panetta’s visit to Afghanistan was marred by a serious security breach yesterday when a stolen vehicle was driven onto a runway ramp as the Pentagon chief’s plane was landing at a Nato base.

US officials insisted there was no sign the incident at Camp Bastion in the country’s south was an attempted attack on Mr Panetta but the carjacking raised questions over security at the fortified base and added to a crisis atmosphere in the Nato-led war effort.

Mr Panetta travelled to Afghanistan just days after a US soldier shot dead 16 villagers – most of them women and children – in southern Kandahar province in the worst single such incident since the 2001 US-led invasion.

The suspect in the massacre, a US Army sergeant who had served three tours in Iraq, had been flown out of Afghanistan, Pentagon officials said yesterday, without saying where he was taken.

The move indicated the suspect would, if charged, be tried in a US military court outside of the war-torn country, despite demands by Afghan political leaders for a public trial in Afghanistan.

The transfer of the shooting suspect could complicate already difficult talks with Kabul on a possible US troop presence after 2014, as President Hamid Karzai’s government has so far refused to grant legal immunity to American troops – the same issue that scuppered a US strategic pact with Iraq.

In the first leg of a two-day visit to Afghanistan, Mr Panetta said recent “troubling” events should not force a change in Nato’s war strategy.

Even as Mr Panetta touted progress on the battlefield, officials reported a hijacked vehicle had made it onto a runway ramp where the Pentagon chief’s plane was due to park at Camp Bastion in Helmand province. At about the same time Mr Panetta’s aircraft was landing at 11 a.m., an Afghan civilian hijacked a pick-up truck from a soldier in the coalition force.

He drove the vehicle at high speed before he crashed into a ditch and emerged in flames, Mr Panetta’s spokesman George Little told reporters in Kabul.