A detective from the Police Commissioner’s office looking to ease tension between Harlem cops and local residents after an alleged brutality incident was denied entry to a notorious mosque simply because he was carrying his gun and shield, The Post has learned.

The embarrassing flap occurred Friday night, when Det. Martin Brown, who is assigned to the Police Commissioner’s Liaison Unit, showed up at Mosque No. 7, at 106 West 127th Street after allegations that local youths were roughed up by cops from the 32nd Precinct, sources said.

When Brown showed up at the mosque — the scene of a horrific 1972 cop killing — the official who had invited him, Abdul Kareem Muhammad, the head of the Harlem Clergy and Community Leaders Coalition, did not let him enter because of his gun and shield, sources said.

“It was a misunderstanding, one borne of ignorance,” said one police official.

Those items are barred under the mosque’s rules of worship – and the news touched off a few minutes of awkwardness as Brown patiently waited outside the mosque.

The mosque’s imam, Abdul Hafeez Muhammad, then greeted Brown and apologized, but reiterated the fact that he would not be allowed inside to attend the meeting, where other community leaders were in attendance, because of his gun and shield.

“He refused to comply with the demand. He wasn’t going to relinquish his weapon,” an NYPD spokeswoman said.

Brown, who was not made aware of the mosque’s rules beforehand, left without fanfare a short time later, sources said.

One police source was less forgiving, insisting it was a slap, however inadvertent, to the Police Commissioner’s authority, particularly since the detective had showed up in act of conciliation and outreach to the Harlem community.

The same mosque was once headed by the Rev. Louis Farrakhan and is the site of one of the most embarrassing chapters in New York City history. On April 14, 1972, Police Officer Philip Cardillo was fatally shot when he and a partner responded to a phony 911 call and were trapped inside by a mob of Nation of Islam members.

(Source: NY Post)