The man was arrested in a raid on a house in Cove, Hampshire. Police confirmed that explosives were present and more than 30 officers sealed off a residential street.

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A man and a woman - both as yet unidentified - died immediately as the blast ripped through the Admiral Duncan pub. Another man died on Saturday afternoon.

It took place in Soho's busy Old Compton Street as Bank Holiday crowds enjoyed a sunny evening. The street has been re-opened but the pub is still cordoned off.

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The nail bomb was the third in two weeks. The first blast shook a busy Brixton market in south London a fortnight ago, injuring 39 people.

It was followed a week later with a second nail bomb in Brick Lane, east London, which injured six people.

Home Secretary Jack Straw visited some of the people still in hospital on Saturday and spoke of his outrage.

The locations of the nail bombs

The Queen sent her sympathies to the 66 people injured - mostly men in their 20s and 30s. Some had limbs blown off and others were seriously burned.

By Sunday morning 19 remained in hospitals across London and the Home Counties.

Some of the injured are expected to be allowed home later in the day, but six people remain in a critical condition.

University College, Middlesex and St Thomas' Hospitals each have two of the critically ill people.

Doctors described the casualties as having suffered "horrific, appalling and devastating injuries".

A vigil for the injured was held on Saturday night in Soho Square, near the scene of the nail bomb. It followed a protest march which united gays and ethnic minorities in anger against the attacks.

Residents evacuated

Right-wing terror group, the White Wolves, has claimed responsibility for the bomb. They also claimed to have carried out the earlier two explosions.

A senior officer from Scotland Yard's Anti-Terrorist Branch said the Hampshire man was arrested as a result of information prompted by a CCTV video still.

Sue Haley reports from Cove in Hampshire

"He is a male in his early 20s and he has been taken to a central London police station in connection with the Brick Lane and Brixton bombs," he said.

Residents in Sunnybank Road, in Cove, were told to grab their children and leave their homes as detectives sealed off a quiet street.

Sharon Wells, who lives three doors away from the house where the arrest was made, said she had been told that explosives were found inside.

She said: "We used to let our children run around but I'm going to ship them out today. We've heard that the house is a bomb factory. It's frightening."

Detectives arrested four other people in connection with the bombings, but they have been freed on police bail.