A Muslim cleric and an associate were on Saturday shot dead by a lone gunman following afternoon prayers at a mosque in the New York City borough of Queens.

Authorities said the gunman approached the men from behind and shot them in the head at close range while they were walking together on a blistering hot afternoon in the Ozone Park neighborhood. No arrest however had been made.

The motive for the shooting was not immediately known and no evidence has been uncovered that the two men were targeted because of their faith, said Tiffany Phillips, a spokeswoman for the New York City Police Department. Even so, police were not ruling out any possibility, she added.

Quoting police source, Reuters reported that the victims identified as Imam Maulama Akonjee, 55, and Thara Uddin, 64, were both wearing religious garb at the time of shooting.

The men were transported to Jamaica Hospital Medical Center where they died, hospital spokesman Andrew Rubin said.

The Council on American-Islamic Relations, a Muslim civil rights and advocacy group known by the acronym CAIR, said Uddin was an associate of the imam.

"These were two very beloved people," Afaf Nasher, executive director of the New York chapter of CAIR, told Reuters. "These were community leaders.

"There is a deep sense of mourning and an overwhelming cry for justice to be served," Nasher said. "There is a very loud cry, too, for the NYPD to investigate fully, with the total amount of their resources, the incident that happened today (Saturday)."

The organization held a news conference on Saturday evening in front of the mosque, the Al-Furqan Jame Masjid, where the two men had prayed.

"We are calling for all people, of all faiths, to rally with compassion and with a sense of vigilance so that justice can be served," Nasher said. "“You can’t go up to a person and shoot them in the head and not be motivated by hatred.”

The suspect was seen by witnesses fleeing the scene with a gun in his hand, police said.

"We are currently conducting an extensive canvass of the area for video and additional witnesses," Deputy Inspector Henry Sautner said in a statement.

Eric Phillips, a press secretary for New York City Mayor Bill de Blasio, said the mayor was closely monitoring the police investigation into the shootings.

"While it is too early to tell what led to these murders, it is certain that the NYPD will stop at nothing to ensure justice is served,” Phillips said in a statement.

In June, CAIR issued a statement calling for Muslim community leaders to consider increasing security after the Orlando massacre and incidents that it said had targeted Muslims and Islamic houses of worship.

A gunman who called himself an "Islamic soldier" killed 49 people in an Orlando, Florida, nightclub on June 12.

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