Legal Affairs Correspondent Joshua Rozenburg reports from the High Court

The claim was made by a lawyer acting for the former Chilean dictator, who said Home Secretary Jack Straw should have intervened straight away and cancelled the provisional arrest warrant against him.

But Alun Jones QC, representing the Crown Prosecution Service, said General Pinochet was lawfully detained.

Mr Jones accused the former dictator of being responsible for the deaths of "at least 4,000 people" and alleged that he had sent agents to Spain to "seek out and kill" political opponents.

Speaking for the general, Clive Nicholls QC said: "It is submitted that any attempt to deny Senator Pinochet immunity will open up the prospect of the Queen being extradited from America to Argentina for the murder of Argentinian nationals killed in the Falklands, or to Ireland for the murder of Irish citizens in Gibraltar."

As the hearing was taking place, a Swiss judge requested the provisional arrest and extradition to Switzerland of General Pinochet.

Michael Caplan QC: Part of the team defending General Pinochet

The Geneva Public Prosecutor Bernard Bertossa said in a statement that the necessary legal conditions had been met to begin an enquiry into the case of a Swiss national, Alexei Jaccard.

Jaccard was arrested by Chilean and Argentinian police in Buenos Aires in 1997. His family blame the former dictator for his subsequent disappearance.

Arrest 'unlawful'

General Pinochet's lawyers have argued that his arrest was not legally justifiedl on several grounds, including immunity from arrest for actions committed while he was head of state.

Mr Nicholls argued that allowing him to go free did not raise the spectre "of a Hitler going unpunished",

Home Affairs Correspondent Jane Peel reports from the court

"The courts of one country cannot sit in judgment on the acts of a government of another country done within its own jurisdiction."

He said the correct form was an international court set up by the UN.

General Pinochet, 82, is being held at a London clinic where he was arrested on 16 October while recovering from major surgery.

Lord Chief Justice Lord Bingham: One of the judges hearing the case

The High Court heard that the original arrest warrant was carried out at the request of Spanish judges.

They want to extradite General Pinochet and try him for genocide and terrorism following alleged abuses that occurred while he ruled the Chile from 1973 to 1990.

Mr Nicholls argued that both the original warrant and an "unprecedented" second warrant issued on 22 October were "fatally flawed" and should have been cancelled by the home secretary.

Mr Nicholls said the second provisional arrest warrant issued by Bow Street chief magistrate Ronald Bartle "did not allege an extradition crime and is bad on its face".

That warrant accuses the former dictator of conspiring with others to "intentionally inflict severe pain and suffering" between 1988 and 1992 "as a public official"; between 1982 and 1992 conspiring to take hostages and threaten to kill them; and also conspiring to commit murder between 1976 and 1992.

Meanwhile, violence broke out at a demonstration in the Chilean capital, Santiago, held on Sunday in support of General Pinochet's arrest.

More than 40 people were arrested as police used tear gas and water cannon to disperse several thousand protesters calling for General Pinochet's trial on charges of torture and genocide.

A Chilean aircraft carrying medical equipment is known to have landed at RAF Brize Norton, sparking speculation that the UK government intended to release General Pinochet "on humanitarian grounds".