A forest of steel pillars was unveiled in London's Hyde Park on Tuesday, honouring the victims of the July 7, 2005, attacks on the city's transit system.

The memorial is for the 52 victims of the bombings of three of London's Underground trains and a bus during the peak of the capital's rush hour.

Fifty-six people, including the four bombers, were killed in the attacks, and more than 700 people were injured.

The columns are grouped to represent the attack sites and the various transit stops where the bombings occurred.

Each of the 52 columns is 3.5 metres tall and uniquely designed to represent the uniqueness of each victim. A nearby plaque displays the names of the victims.

British Prime Minister Gordon Brown, London Mayor Boris Johnson and Prince Charles attended the fourth anniversary memorial service in Hyde Park, along with families of the victims.

"I believe the date of the London bombings is etched vividly on all our minds as a brutal intrusion into the lives of thousands of people," Prince Charles said.

Place to mourn

"I do pray that all those touched by the violence everywhere will eventually find peace again," the Prince of Wales told the attendees. "Above all, I pray they will gain comfort and strength from coming together to honour the memories of those taken from us."

The memorial will provide a place for victims' families and all Britons to gather to reflect on the attacks and those who died, said British Humanitarian Minister Tessa Jowell.

The family of the victims and those injured in the attacks were involved in determining the design and location of the memorial.

Ken Livingstone, who was London's mayor at the time of the attack, praised the design of the statues.

"I think it's just exactly right. Often, it's very difficult to do something like this and get it right," he said.