Thatcher and Opponents Blame Extremists : Tax protest: Scuffles flare anew as an official inspects damage at Trafalgar Square.

Prime Minister Margaret Thatcher and opposition politicians blamed extremist groups Sunday for turning a carnival-like tax protest into one of London’s worst riots this century.

Meanwhile, the new local tax went into effect in England and Wales. In London, scuffles erupted when Home Secretary David Waddington inspected riot damage. Four people were arrested.

Saturday’s protest by 40,000 people in Trafalgar Square went amok when militants smashed windows, torched cars and battled police. Hundreds of people were injured.

The so-called community charge replaces a property tax with a flat levy on everyone over the age of 18, increasing the amount many pay by up to a third. Critics charge that it is unfair.

Thatcher told reporters of her “absolute horror” at Saturday’s violence as she left church at her country residence at Chequers.

“People have a right to demonstrate peacefully. This was taken over by some extreme groups who used violence with no consideration for others or their property,” she said. “Let us hope that justice will be seen to be done.”

Labor Party chief Neil Kinnock said those who caused the violence must be “treated as criminals” and punished.

“As always, they damaged freedom and like every other democrat, I regard them and treat them as enemies of freedom,” said Kinnock, whose party is 28 points ahead of the Conservatives in opinion polls.

Scotland Yard launched a top-level investigation into the six-hour street battle, which sent 58 police and 75 civilians to the hospital, injured 22 police horses and caused hundreds of thousands of dollars of damage.

Detective Chief Supt. Roy Ramm, leading the investigation, said 341 people were arrested for offenses including arson, robbery, serious assault and looting.

On Sunday, as many as 200 people shouted angry abuse as police escorted Waddington past boarded-up windows, piles of shattered glass and wrecked cars.

Many properties damaged Saturday were among Britain’s most exclusive names: Liberty’s, Burberrys, Mappin & Webb, Dickens & Jones.

In Trafalgar Square, black smoke was still rising from construction cabins on the side of a seven-story building undergoing renovation that had been set on fire by the protesters. The South African Embassy across the street also was fire damaged.

David Meynell, Scotland Yard’s deputy assistant commissioner, blamed the “sustained and savage violence” on about 3,500 people who were among the crowd of 40,000 at Trafalgar Square. Organizers put the crowd at 200,000.

Meynell said the clashes began when demonstrators heading up Whitehall to Trafalgar Square stopped at the corner of Downing Street, where Thatcher has her official residence, and tried to storm the barricaded entrance to the street. The riot eventually spread to the West End theater district.

Of those injured, he said, two police officers and two civilians remained hospitalized.