A British man has been arrested in London at the request of US authorities who allege he ran websites which helped raise money for terrorism.
The allegations do not relate to domestic terrorism in the UK
Officers arrested Syed Talha Ahsan, 26, at his home in Tooting on a federal indictment from the district attorney of the state of Connecticut.
Authorities there said an internet server based in the state was used.
He was remanded into custody after appearing at Horseferry Magistrates Court on Wednesday afternoon.
A police spokesman said he was being held in a central London station.
'Several years' investigation'
The indictment charged him with conspiracy to support terrorists and conspiracy to kill or injure people abroad.
"These charges are the result of several years of investigative work by ICE and FBI agents in New Haven, NCIS agents, and several additional law enforcement partners here in the United States and overseas," Connecticut district attorney Kevin O'Connor said.
Mr Ahsan is accused in the same case as Babar Ahmad, who was arrested in Connecticut in October 2004, over the publication of sites including Azzam.com, which are accused of supporting organisations such as al-Qaeda.
Mr Ahsan and Mr Ahmad are alleged to have operated internet sites in Connecticut, Nevada, the United Kingdom, Ireland and Malaysia encouraging people to donate money or equipment.
They have also been accused of helping terrorists find short-term residence in London and to help them gain entry to zones of conflict such as Afghanistan and Chechnya.
Mr Ahmad has been fighting extradition to the US for the past two years.