LONDON — An attacker entered London Central Mosque during afternoon prayer and stabbed a 70-year-old prayer leader on Thursday, before being subdued by worshipers and arrested on suspicion of attempted murder, the police said.

People who attend the mosque regularly said they were familiar with the suspect, and the Metropolitan Police said they were not treating the stabbing as an act of terrorism. The victim’s wound was not considered life-threatening, the police said.The injured man was a muezzin, the person who leads the call to prayer, and he had just begun singing when he was assaulted, the mosque said in a statement.

“The attacker was apprehended by the worshipers until the police arrived and arrested him,” the mosque’s statement read.

Magdi Yousef, a regular worshiper who witnessed the assault, said the suspect was a friend of the victim’s, and that he often saw the two of them together.