London, England - Six men, including radical Muslim Abu Izzadeen, have been arrested over speeches made at a mosque two-and-a-half years ago.
Scotland Yard said the men were detained in an investigation into incitement of others to commit acts of terrorism overseas and terrorist fundraising.
The men, aged between 21 and 35, were held at addresses in east London, Southall and Luton at around 5am.
The speeches were allegedly made at a mosque in London in November 2004.
A Yard spokesman said a number of searches were ongoing in connection with the investigation.
He said: "The arrests form part of a long-term pro-active and complex investigation into alleged incitement and radicalisation for the purposes of terrorism, as well as alleged provision of financial support for international terrorism."
Izzadeen, a former electrician who lives in Leytonstone, east London with his wife and three children, is perhaps best known for his barracking of Home Secretary John Reid last September.
At a speech to British Muslims in Leyton, east London, Mr Reid was interrupted by Izzadeen, who called him "an enemy of Islam" and "a tyrant".
He also accused the British Government of state terrorism and said Prime Minister Tony Blair and US President George Bush could "go to hell".
He was also reportedly involved in protests against the Danish anti-Muslim cartoons and has been linked to radical Islamic group al-Ghurabaa, an offshoot of al-Muhajiroun, both of which are now banned in the UK.