ISLAMABAD - A volunteer American cardiologist of Pakistani origin was shot dead in a remote Pakistani town on Monday, in the latest attack which underscored growing religious hatred across the south Asian country.

Doctor Mehdi Ali Qamar, who a Pakistani official said lived in Columbus, Ohio, and was visiting a family graveyard in the town of Chenab Nagar in Pakistan's Punjab province early morning on Monday, was shot by two gunmen riding a motorcycle.

He belonged to the Ahmadi sect of Muslims whose members were officially declared to be heretics under Pakistan's law in the mid-1970s. Qamar was a naturalized U.S. citizen who moved there about 15 years ago but visited Pakistan occasionally for volunteer work, said a senior police official in Pakistan's city of Lahore, which is the local capital of the Punjab.

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Qamar was accompanied by one of his cousins and a 5-year-old son when he was attacked, the police official said, who was speaking to CBS News on condition of anonymity because he was not authorized to speak to journalists. Qamar's companions were not hurt.

"The assassination of Dr. Qamar took place apparently because he belonged to the Ahmadi sect," said the police official adding that the doctor was in Pakistan to perform medical procedures as a volunteer.

The Ahmadi movement is regarded by orthodox Muslims as heretical because it does not believe that Mohammed was the final prophet sent to guide mankind.

The U.S. Embassy in Islamabad confirmed the attack and the identity of the victim. Meghan Gregonis, a U.S. Embassy spokeswoman, said in a statement: "We express our deepest condolences to his family and friends. The U.S. Embassy is providing consular assistance. Out of respect for Dr. Qamar's family during this difficult time, we have no further information to share."

Qamar's killing was the latest in scores of attacks carried out by hardline Islamists targeting members of the Ahmadi community. Members of other groups, including Shia Muslims, have also been killed in attacks carried out by hardline members of the Sunni Muslim community, which represents Pakistan's majority population.

Analysts warned the killings suggest a dangerous trend for the security of the south Asian country.

"These killings are of course driven by insanity. But they will continue to increase Pakistan's internal conflict," said Ghazi Salahuddin, a commentator for the English-language "The NEWS" newspaper, in an interview with CBS News.

Salahuddin added that "urgent action must be taken to curb all groups involved in senseless killings of the kind we have seen in Dr. Qamar's case. Otherwise, there will be more bloodshed."

Western diplomats in Islamabad warned killings of innocent people are likely to grow across Pakistan in the coming months as the U.S. prepares to withdraw its forces from Afghanistan, a move that many have predicted will provide encouragement to members of hardline Islamic groups like the Taliban.

"Many Islamic militants have connections to the Taliban. When U.S. forces leave this region, they will feel encouraged, " said one Western diplomat in Islamabad who spoke to CBS News on condition of anonymity. "It is vital for the Pakistani government to investigate every such killing in great detail and nail down those responsible. You can't allow these people to feel they are increasingly above the law. "