KABUL, Afghanistan — A suicide bomber in a car packed with explosives struck a British Embassy vehicle Thursday, killing six people, including a British civilian security officer, and wounding more than 34. An Afghan working for the embassy was killed and a second British member of the security team was among the injured, according to a statement from the U.S.-led military coalition in Afghanistan. Later, two suicide bombers set off their explosives near the office of an international nongovernmental organization in Kabul’s diplomatic neighborhood, injuring a foreign national, Afghan officials said.