Even in a country wracked by violence for decades, the killing of a senior Afghan Sufi religious leader and 10 other men stands out from the statistics: shot in the backs of their heads while bowed in prayer, in a ruthless and apparently well-planned operation.

The attack Saturday night has mystified authorities and a government investigation has come up empty handed, with no suspects so far, Interior Ministry spokesman Sediq Sediqqi said. Afghan President Ashraf Ghani on Thursday ordered a report on the probe, according to his spokesman, Ajmal Abidy.

Attacks on mosques are rare in Afghanistan, even with a history of enmity between the majority Sunnis and the Shiites who make up about 15 percent of the population.

Sufism is considered a mystical branch of Islam in which followers seek a direct personal relationship with God. Best known for the "whirling dervishes" who spin in a trance, Sufism developed alongside mainstream Islam. It is widely admired for its philosophy of tolerance and forgiveness, and includes free thinkers, scientists and poets, including Rumi and Omar Khayyam.

In Afghanistan, Sufis are among the tiny communities of religious minorities that also include Ismaelis, Hindus, Sikhs and a Jew. An unknown number of Christians practice secretly, fearing persecution despite a constitutional guarantee of religious freedoms.

The shootings at the mosque, built behind a parking lot in a shabby western suburb of the capital, Kabul, took place as Pir Saheb Mohammed Bahadur Jan led the evening prayers.

"As they were kneeling for the second round of praying, men armed with small handguns fitted with silencers came in and shot everyone from behind," said the prayer leader's son, Abdul Waheed Bahaduri.

He was recounting the scene described to him by the sole survivor of the attack, Ahmad Zia. Bahaduri had gone home to pray because there was no electricity at the mosque. The prayer room was lit by the dull flame of a gas lamp.

Zia survived by hiding under the bodies of the others, said Abdul Nahim Ahmadzai, a close friend of the Bahadur family. "He told us later that a gunman shouted in Pashto: 'No one should be left alive'," Ahmadzai said, referring to the language of southern Afghanistan, where the Taliban originated.

Following the attack, Bahaduri's father and older brother Shah Agha Jan, also a senior Sufi leader, were buried in fresh graves in the center of the mosque's concrete courtyard. With their deaths, the 28-year-old Bahaduri is now leader of 100,000 Sufi Muslims scattered throughout Afghanistan.

Sitting cross-legged on a crimson carpet, his brother's three young sons nearby, Bahaduri was incredulous that no senior government official had visited the mosque or contacted him since the attack.

"I want the president to come here and talk to us about this," he said. "It was 11 people, killed in a mosque while they prayed."

Still, in a country where everything from gender to ethnicity is politicized, Bahaduri refused to accept that the attack was politically motivated. "We are very peaceful people. My father had followers all over the world and he welcomed people here from wherever they came from and whatever religion they were," he said.

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Associated Press writer Amir Shah in Kabul contributed to this story.

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