He launched into a furious tirade at the Jabir Bin Zayd mosque in Barking, east London, claiming voting was wrong.
The mosque's manager said last night: "He started saying that voting was un-Islamic and we shouldn't do it.
"He got very angry. I called him aside and said, 'Please calm down'. He refused, so I removed him. Thank God he followed me.
"When we got outside the room, he said: 'You don't have authority over me, only God has authority because this is a house of God'.
"I said: 'That might be true, but I am in charge'."
The ISIS extremist reportedly interrupted a sermon by ranting about voting Morning after London attack: Heightened police presence at Borough Market & Bridge Sun, June 4, 2017
SIX people have been killed after a horrific terror attack targeted London Bridge and Borough Market on Saturday night. These are the pictures are London wakes up to the tragic scenes
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He seemed to have no knowledge of religion
The manager said the terrorist, who was shot dead after his rampage through the capital on Saturday night, knew little about Islam.
Speaking to the Mail, he added: "He had no special friends here. He would arrive, pray and then leave.
"He said hello to people but generally kept himself to himself. He seemed an uneducated person. He seemed to have no knowledge of religion."
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He was removed from the Jabir Bin Zayd mosque in Barking after the outburst
Seven people were killed in the atrocity on London Bridge and in the area around Borough Market, with a further 48 injured.
The first victim of the terror attack was this morning named as 30-year-old Canadian national Christine Archibald.
In a moving statement, her family said: "She had room in her heart for everyone and believed strongly that every person was to be valued and respected."
Seven people were killed in the attack, including 30-year-old Christine Archibald
Canadian Prime Minister Justin Trudeau said he was "heartbroken" to learn of Ms Archibald's death.
He added: "These hateful acts do not deter us; they only strengthen our resolve. Canadians stand united with the British people.
"We will continue to work together with the United Kingdom and all our allies to fight terrorism and bring perpetrators to justice."