KABUL - Insurgents fired two rockets at the main NATO airbase in Afghanistan, damaging an aircraft used by US Joint Chiefs of Staff chairman Martin Dempsey, a NATO spokesman said on Tuesday. The general was not on board at the time.Dempsey arrived in the country on Monday in a C-17 transport aircraft which was parked at Bagram Airbase, north of Kabul, when two rockets landed near the apron late on Monday night, slightly wounding two ground staff."He was nowhere near the aircraft. We think it was a lucky shot," NATO senior spokesman Colonel Thomas Collins said.The aircraft was only being used temporarily by Dempsey and his staff. The rockets also damaged a nearby helicopter.Dempsey, who had been in the country for talks with NATO and Afghan commanders on a string of recent rogue shootings, left the country on another aircraft.Bagram is occasionally targeted with rockets and mortar shells fired by insurgents from surrounding hills and fields.Sporadic attacks also occur at NATO's other main airbase in Afghanistan, Kandahar Airfield, in the volatile south, although they rarely cause deaths or major damage.Before leaving Afghanistan, Dempsey met his Afghan counterpart, General Sher Mohammad Karimi, who raised the issue of insider attacks by rogue forces that have killed 10 American troops in the past two weeks."In the past, it's been us pushing on them to make sure they do more," he said on Monday. "This time, without prompting, when I met General Karimi, he started with a conversation about insider attacks - and, importantly, insider attacks not just against us, but insider attacks against the Afghans, too."