Senior Pakistani officials have confirmed that Ramzi Binalshibh, a key al-Qaeda suspect arrested in a raid in Karachi last week, is now in US custody.

Mr Binalshibh is accused of being one of the main planners of the 11 September attacks on America.

Ramzi Binalshibh is alleged to have helped fund the hijackers

The officials says he was flown out of the country to an undisclosed location, which the BBC's Karachi correspondent, Zaffar Abbas, says is probably a US warship or base in the region, possibly in Oman.

Four other al-Qaeda suspects who were captured with Mr Binalshibh last week after a gun battle in the city were also flown out, the officials said.

The Pakistani Interior Minister, Moinuddin Haider, told the BBC the handover showed Pakistan's willingness to co-operate with the United States in its campaign against terrorism.

He said the operation had been a great success and he was confident that other al-Qaeda suspects hiding in Pakistan would be caught.

The suspects now in US custody have already been questioned by the Pakistani and American intelligence services.

Senior figure

Mr Binalshibh is the most significant figure they have captured since Abu Zubaydah - an alleged associate of Osama bin Laden arrested in Pakistan in March.

Mr Binalshibh has been charged in Germany over his alleged role in planning last September's attacks.

He shared a house in Hamburg with Mohammed Atta, the man thought to be the ringleader of the suicide hijackers.

Binalshibh was arrested after a three-hour gunfight

Investigators believe he would almost certainly taken part in the attacks, but was repeatedly denied a US visa.

The German authorities were keen to question him but the country's interior minister, Otto Schily, on Sunday said the American request for his extradition had priority.

Mr Binalshibh is thought to have been involved in other attacks blamed on al-Qaeda - including the bombing of a synagogue in Tunisia in April, and the suicide bomb attack against an American destroyer, the USS Cole, in Yemen in 2000.

The five other men and two women, who were also arrested in the raids in Karachi, are remaining in the country.

The Pakistani authorities have said that they do not believe these seven to be key al-Qaeda members, but they will continue to questions them to try to rake up intelligence on the whereabouts and plans of other al-Qaeda operatives.

Intelligence

The Bush administration had made it clear that they wanted custody of Mr Binalshibh.

On Sunday the US national security adviser, Condoleeza Rice, said: "There's no doubt that the United States will want to have access to him and to have him, because this is an important breakthrough."

The interrogation of Abu Zubaydah - who is being held by the Americans at an undisclosed location - is reported to have been difficult.

But BBC Middle East analyst Roger Hardy says information he has provided has led investigators to identify other members of the group.

Our correspondent says US officials hope Mr Binalshibh will do the same.