The man, who the U.S. embassy declined to identify, works for the consulting firm J.E. Austin Associates Inc., and was working on a development project in the country's lawless tribal areas, where Pakistani troops have been battling Islamist insurgents for years.
A U.S. embassy spokesman said they were trying to confirm the reports.
"Some six to eight people broke into his house at around 3:30 a.m., when security guards on duty were making preparation for fasting," police official Tajamal Hussain told Reuters, referring to the Ramadan fast observed by Muslims.
"Two of the assailants came from the front gate while about six others used the backdoor. They tortured the guards and then took the American with them."
A security official familiar with the incident said the gunmen forced the man's driver to knock on his bedroom door. When the man opened it, they took him.
Hussain said the man, in his 60s, had been living in Pakistan five to six years. He mostly lived in Islamabad but had been traveling to Lahore.
The security official said there has been no claim of responsibility.
Kidnap for ransom is relatively common in Pakistan, though foreigners are not often targets. Militants also occasionally take foreigners hostage.
Pakistani Taliban, linked to al Qaeda, have claimed responsibility for kidnapping a Swiss couple in July in the volatile southwestern province of Baluchistan.
They said the couple could be freed in exchange for a Pakistani woman serving a jail term in the United States for shooting FBI agents and U.S. soldiers in Afghanistan.
Eight Pakistani employees of a U.S.-based aid organization, American Refugee Committee (ARC), were kidnapped in Baluchistan last month.
Anti-U.S. sentiments runs high in Pakistan, and already prickly ties between Islamabad and Washington hit a low point after the May 2 killing of al Qaeda chief Osama bin Laden in an attack that Pakistan termed a breach of its sovereignty.