An investigation by a security analysis group has found evidence of Islamic extremists operating at a university in London. Activities on university campuses have been under scrutiny by UK authorities after Omar Farouk Abdulmutallab, a Nigerian man allegedly tried to blow up an airliner bound for Detroit last Christmas Day. He spent three years studying at a university in London including time as the president of the university's Islamic Society.

City University London is one of the capital's most prestigious institutions, attracting students from across the world.

But a new investigation claims that some members of the university's Sunni Islamic Society or 'ISoc' hold extreme interpretations of Islam - and that they are trying to radicalize Muslims on campus.

The report was partly based on recordings of Friday prayer sermons by the President of the Islamic Society. "When they say to us 'the Islamic state teaches to cut the hand of the thief', yes it does! And it also teaches us to stone the adulterer?When they tell us that the Islamic state tells us and teaches us to kill the apostate, yes it does!," Saleh Patel said in one recording.

Lucy James, from the Quilliam Foundation, led the investigation. She says some members of the Islamic Society are encouraging violence. "There were also more intolerant and verging on violent forms of Islam that were being espoused. For example that people who don't pray five times a day should be murdered and inviting preachers on campus who thought that homosexuals should be thrown off mountain tops. So it was an extreme form of Wahhabism mixed with a political form of Islamism that made quite a fiery concoction," she said.

Quilliam's investigation also found inflammatory images on the Sunni Islamic Society's website attacking Shia Muslims who were called rejectionists.

City University's Islamic Society was approached for an interview but did not respond.

The failed attack on a Detroit-bound airliner last Christmas brought the issue of Islamic radicals at British universities into sharp focus.

The alleged bomber, Nigerian Omar Farouk Abdulmutallab, spent three years at University College London, becoming president of the Islamic Society in his second year.

He later studied in Yemen and al-Qaida operatives are believed to have helped plan the attack.

UCL has just completed its own investigation into Abdulmutallab's time at the university.

Professor Anthony Finkelstein says the evidence suggests Abdulmutallab was not radicalized at UCL. "The most exceptional thing that people remembered is how unexceptional he was. He was a diligent student who completed his studies satisfactorily," he said.

Professor Finkelstein says balance must be struck between guaranteeing the freedom to debate, while making sure so-called preachers of hate are kept off campus. "Our students are clever young men and women, often at vulnerable times in their lives, making personal transitions of all sorts. Therefore it is inevitable that they are the potential targets of those who wish them and us ill," he said.

Rashid Ansari, an executive member of the Federation of Student Islamic Societies, says such societies are not being hijacked by extremists. "Islamic societies are probably the most open and democratic societies on campus and the most widely scrutinized societies on campus, because with this horrendous narrative of extremism and radicalization taking place, being purported by spurious think-tanks and right-wing media, they're hugely under the spotlight," Ansari said.

University authorities say they cannot and should not police every student activity. But increasingly those authorities are on the frontline of the battle to prevent the spread of extremist views.