Radical Islamic cleric Abu Hamza al-Masri was part of a global terror network which plotted Jihad against the west, a hearing has been told.
The US is seeking the extradition of Abu Hamza
On the first day of extradition proceedings against him in London, Abu Hamza, 48, was accused of involvement in the kidnap of westerners in Yemen.
The claims were made on behalf of the US government, which wants to try him.
But Abu Hamza's barrister said some of its evidence was obtained by torture and the application should fail.
The Egyptian-born cleric, who formerly preached at Finsbury Park Mosque in north London, faces 11 terror charges in the US, which carry a potential jail sentence of 100 years.
He is currently serving a seven-year jail term in the UK for soliciting murder and inciting racial hatred.
Hugo Keith, representing the US government, told the hearing at Woolwich Crown Court: "The general allegation is that Mr Hamza is a member of a global conspiracy to wage Jihad against the US and other western countries.
"Jihad carried out in numerous parts of the world - the UK, Afghanistan, Yemen and US.
"He advocated the defence of Islam through unlawful, violent and armed aggression in order to influence the US government."
Mr Keith said that a group of westerners including 12 Britons, two Americans and two Australians were abducted in Yemen in 1998, partly in order to gain the release of Abu Hamza's stepson Mohsen Ghailan and five others.
The hearing was told that Abu Hamza gave advice to the hostage-takers and provided them with a satellite phone.
Four of the captives - Britons Margaret Whitehouse, 52, a teacher from Hampshire, Ruth Williamson, 34, an NHS employee from Edinburgh, university lecturer Peter Rowe, 60, from Durham, and Australian Andrew Thirsk - were killed after Yemeni authorities tried to rescue them.
'Abuse of process'
The hearing was told that Abu Hamza provided expenses for Feroz Abbasi, one of the former British Guantanamo Bay detainees, to travel to Afghanistan.
The cleric is also accused of helping fund another man's visit to a terrorist training camp in the Middle East, and helping set up a similar camp in Bly, Oregon, in the US.
Abu Hamza missed the morning session at Woolwich Crown Court because he was recovering from an operation to remove an inch of bone from his arm.
He attended the hearing in the afternoon session but sat with his head bowed and the stump on his left arm was heavily bandaged.
Alun Jones, QC, for Abu Hamza, said the evidence against his client had been obtained by torture.
Mr Jones added: "This means the extradition request constitutes an abuse of process of the court and shouldn't be received."
The House of Lords paved the way for the case after refusing Abu Hamza leave to appeal against his convictions.
The hearing, which is expected to last a further three days, was adjourned.