KABUL - US air strikes "may have" hit a hospital run by Medecins Sans Frontieres (MSF), a NATO forces spokesman said, after the medical aid group blamed an aerial attack for the destruction in the northern Afghan city of Kunduz that killed three staff.US forces conducted an air strike in the city at 2:15 a.m. on Saturday, Col. Brian Tribus, a spokesman for the NATO-led coalition, said in a statement on Saturday."The strike may have resulted in collateral damage to a nearby medical facility," he said. "This incident is under investigation."Dozens of staff were still missing after the attack that partially destroyed its trauma center, MSF has said.