Kabul, May 02 (ANI): At least six people have been killed in a suicide car bomb attack in Afgan Capital today, hours after U.S. President Barack Obama left Kabul, following an unannounced visit, coinciding with the first anniversary of the military raid that killed Osama bin Laden. Obama made an unannounced visit to Afghanistan to sign a strategic pact with Afghan President Hamid Karzai and to deliver an election year message to Americans that the war is winding down.