Tonight is going down as one of those black nights in history

Leeds United chairman Peter Ridsdale visited the Taksim Hospital, where Mr Loftus was taken.

Uefa officials decided the semi-final match should still go ahead after a late-night meeting with police chiefs.

Violence broke out about 2030BST after a Leeds fan reportedly insulted a van driver - a knife was drawn and a fan, named by the Foreign Office as Christopher Loftus, 37, was stabbed. A second fan, Kevin Speight, died later in hospital.

About 500 Leeds have tickets for the match at the notoriously intimidating Ali Sami Yen Stadium, which Turkish fans refer to as "hell".

They have been told to stay in their hotels during the day and to seek a police escort to the match.

Mr Risdale added: "Tonight is going down as one of those black nights in history."

FA spokesman Steve Double said: "We're obviously very worried and deeply saddened for all concerned."

Violent scenes

Turkish television station A-TV showed English fans lying in pools of blood in Taksim Square, in the centre of Istanbul's entertainment district.

One man was being given the kiss of life by a policeman in the middle of the road.

Another Leeds fan was lifted by police into a police car to be taken to hospital.

While police tried the clear the area, there were angry scenes, with Turks standing outside restaurants and hotels shouting at the Leeds fans.

The TV pictures showed a middle-aged man with a Yorkshire accent refusing police help for an injury to his thigh.

He shouted at police: "Go away, I'm alright."

Seconds later he was forcibly bundled into a police car.

A lot of the anger appeared to be aimed at the police, who called for reinforcements, according to the report.

Fans on both sides were said to have used an array of weapons.

History of clashes

Several hundred Leeds fans were due to fly to Istanbul from Leeds Bradford airport at 0700BST on Thursday. That flight has now been cancelled.

Manchester United fans ran into trouble when their side played Galatasaray in Istanbul in 1993.

More than 200 fans were arrested and many more were denied entry to the stadium.

There are fears not only of violence at Thursday night's match but also at the second leg at Elland Road.

Websites frequented by hooligans have been inundated with messages vowing to avenge the two dead Leeds fans at the second leg.

There are also fears that the killings could spark trouble between English and Turkish fans during Euro 2000. Turkey's first match, against Italy, takes place in Arnhem on 11 June while England play the following day, against Portugal, in nearby Eindhoven.