LAHORE, Pakistan — The case of Raymond A. Davis, a former United States Special Forces soldier who is being held in connection with the deaths of two Pakistanis, has stirred a diplomatic furor, sending the precarious relationship between the United States and Pakistan to a new low, both sides say.

Mr. Davis, 36, was driving in dense traffic in this city on Jan. 27 when, he later told the police, two Pakistani men on a motorcycle tried to rob him. He shot and killed both and was arrested immediately afterward by police officers who say he was carrying a Glock handgun, a flashlight that attached to a headband and a pocket telescope.

The mystery about what Mr. Davis was doing with this inventory of gadgets has touched directly on Pakistani resentments that members of the large American security presence here roam the country freely and are not answerable to the Pakistani authorities.

The Pakistani press, dwelling on the items in Mr. Davis’s possession and his various identity cards, has been filled with speculation about his specific duties, which American officials would not discuss. Mr. Davis’s jobs have been loosely defined by American officials as “security” or “technical,” though his duties were known only to his immediate superiors.