ALEXANDRIA, Egypt : A US citizen was stabbed to death in the Egyptian city of Alexandria on Friday during clashes between supporters and opponents of President Mohamed Mursi, a doctor and three security officials said.A US embassy official said: "The US embassy has heard of the reports of the death of an American citizen and is seeking to confirm them."The man died from a stab wound to the chest, said General Amin Ezzeddin, a senior Alexandria security official.He said that the young American was using a mobile phone camera near an office of Mursi's Muslim Brotherhood when it was being attacked by protesters. He was rushed to a military hospital, where he died.The account was confirmed by Ibrahim al-Roubi, head of the emergency unit in the Alexandria health department, and by two other security officials.