Wednesday, July 13 2005 15:03 Hrs (IST) - World Time -

London: Investigators are focussing on finding the mastermind of last week's deadly attacks in London, who they believe guided the British men of Pakistani origin to carry out the bombings that killed 52 people.

Detectives believe three of them died carrying out the first attack of its kind in the United Kingdom.

The fate of a fourth man on the bombed Piccadilly Line train remained unclear. One man was arrested in West Yorkshire, where three of the suspects were from.

Terrorism experts say the men may have been guided by a "controlling hand".

In a sensational revelation, police last night (July 12, 2005) said at least three of the bombers are believed to be British men of Pakistani origin who lived in West Yorkshire in Leeds.

Police said they believe four men, including the three Pakistani origin persons who arrived at King's Cross on Thursday morning on a train from Leeds were behind the terrorist bomb attack.

According to images in CCTV, the four young Asian men carried rucksacks and chatted away as they strolled down the concourse towards the Underground at King's Cross station.

Police said the four had earlier met at Luton train station. Carrying rucksacks packed with explosives, they boarded the 0748 hrs (IST). Thames link train and arrived at King's Cross in north London at 0820 hrs (IST).

As planned the four split at King's Cross tube station, each going their separate ways with their weighty rucksacks.

The three friends, aged 30, 23 and 19, had travelled from Leeds, West Yorkshire, having picked up the mobile bombs, probably from a house in the Burley district of Leeds.

The 30-year old got on to the Circle line train and headed west, travelling four steps to Edgware Road station.

At 0850 hrs (IST), the agreed time for the attack, just as the train was pulling out of the station he detonated the bomb.

Seven people died in the blast and more than 100 were wounded.

At the same time the 23-year-old, believed to be Shahzad Tanweer, who had travelled in the opposite direction on the Circle line was between Liverpool Street and Aldgate he set off the high-explosive bomb, killing at least seven people.

The suicide bomber travelled south on the Piccadilly line and had travelled several seconds out of King's Cross station on his way to Russell Square when he detonated his device.

This explosion in the narrow confines of a deep-lying tunnel caused the greatest injuries and kiled more than 21.

The bomber is thought to be among the dead, although the police have yet to identify him among the mass of body parts to be recovered from the scene.

The youngest of the group, Hasib Hussain, 19, is thought to have planned to head north, but the Northern line was closed so he headed to the street above King's Cross and took a No 30 double decker bus.

It was nearly an hour later, at 0947 hrs (IST) that he set off his bomb in Tavistock Square, killing at least 13 people.

The first the police became aware of any of the killers was when Hussain's parents contacted the Scotland Yard emergency helpline at about 10 pm on Thursday to report that their son had been travelling to London with three friends and had not been heard of since.