An Australian Muslim sheikh who campaigns against Islamist extremism says unchecked multiculturalism is to blame for the London terrorist attacks that have killed six people.

Adelaide Shia imam Sheikh Mohammad Tawhidi posted his call on Twitter following the United Kingdom's third jihadist attack in 10 weeks.

'Terrorism in the UK is growing week after week. Having extremists within our societies is not multiculturalism, it's suicide,' he tweeted to his 34,200 followers on Sunday.

He also supports One Nation leader Pauline Hanson's call to ban Islamic migration.

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Sheikh Mohammad Tawhidi says 'unmonitored multiculturalism' is to blame for terrorism

The Shia religious leader said 'unmonitored multiculturalism' was to blame for terrorism

The Iranian-born religious leader, who moved to Australia from Iraq aged 12, later told Daily Mail Australia 'unmonitored multiculturalism is to blame'.

'We need to make sure that those coming into the West really want to be part of the West,' he said.

His calls comes after police in London shot dead three jihadist terrorists who had killed six people and injured at last another 48 during a van and knife rampage in central London.

The sheikh took to social media as Senator Hanson tweeted: 'Stop Islamic migration before it is too late.'

Sheikh Mohammad Tawhidi backs Pauline Hanson's call to ban Islamic immigration

The Shia imam's call to ban Muslim migration from the Middle East echoes aspects of Pauline Hanson's policy proposal

Sheikh Mohammad Tawhidi and Pauline Hanson want Islamic migration banned in some way

Asked about her call, Sheikh Tawhidi said the idea had merit although he stopped short of advocating a ban on all Muslims.

'I support a temporary ban on Muslims coming from the Middle East,' he said.

Sheikh Tawhidi said jihadists had a history of attending mosques that promoted sharia law - hardline Islamic law derived from the Koran and the Hadith, covering the life of the Prophet Mohammad.

'The majority of mosques advocate for sharia law without removing the violent parts,' he said, adding the imam who preached to the three London terrorists needs to be held responsible.

Tawhidi said he had not had contact with Pauline Hanson but would support any policy that strengthened national security.

Sheikh Tawhidi (pictured right) backs Pauline Hanson's call to ban Islamic immigration

Sheikh Mohammad Tawhidi said it was wrong for the Left to link terrorism with unemployment

A Shia imam from Adelaide said the London terror attack was about attacking the West

'You need to investigate and shut down the mosque that this terrorist used to attend.'

The 34-year-old imam said the political Left in the United Kingdom had allowed London to turn into Baghdad.

'The Left wants us to believe that terrorism is the result of unemployment,' he said.

'Since when did humans blow themselves up for not having a job?'

Armed police swooped on the London Bridge area of the UK capital after two incidents, which saw six people killed and dozens injured.

It came after three jihadi terrorists killed six people and injured at least another 48 others during a knife rampage.

The men 'of Mediterranean origin' had shouted 'This is for Allah' after they had mowed down 20 revellers in a white van hurtling across the London Bridge.