Prince William (2nd R) arrives at Manchester Cathedral during the national service of commemoration to remember the victims of the bomb attack in Manchester, Britain, on May 22, 2018. Prince William and British Prime Minister Theresa May joined thousands of people who gathered in Manchester Tuesday on the first anniversary of a terror attack in the city which left 22 people dead. (Xinhua/Craig Brough)

LONDON, May 22 (Xinhua) -- Prince William the Duke of Cambridge and British Prime Minister Theresa May joined thousands of people who gathered in Manchester Tuesday on the first anniversary of a terror attack in the city which left 22 people dead.

The Prince and May were among the congregation at a packed Manchester Cathedral where a special service was held to remember the victims of what was one of worst bomb attacks on the British mainland since World War II.

Colored candles, one for each of the victims aged eight to 51, flickered serenely on the altar during a multi-faith service which was also attended by Labor leader Jeremy Corbyn, Liberal Democrat leader Vince Cable and the First Minister of Scotland Nicola Sturgeon. One of the readings was given by Prince William.

A choir sang the song "Somewhere over the Rainbow", and the Dean of Manchester Rogers Govender said lives had been lost and lives had been changed forever by the attack.

Families of those killed as well as survivors of the attack at the Manchester Arena on May 22, 2017, were also at the service, along with rescue workers who were first on the scene of the tragedy.

As well as the 22 killed, ten of them aged 19 or under, a further 800 were injured physically or psychologically, and many of the rescue workers have been left traumatized.

A one-minute silence was observed in the cathedral, across the city and in public buildings across the country.

Buses in Manchester pulled over by the roadside, and MPs in the House of Commons stood in silence.

High security was in place in and around the city center, with armed cops on duty as many people gathered in public squares to commemorate the anniversary.

The attack came at the end of a concert by U.S. singer Ariana Grande who sent a message Tuesday to the people of Manchester.

It read: "I love you with all of me and am sending you all of the light and warmth I have to offer on this challenging day."

May, writing Tuesday in the Manchester Evening News, said the targeting of the young and innocent as they enjoyed a care free night out in the Manchester Arena was an act of sickening cowardice.

"It was designed to strike at the heart of our values and our way of life, in one of our most vibrant cities, with the aim of breaking our resolve and dividing us. It failed," she said.

Britain's interior minister, Home Secretary Sajid Javid, said: "Today my thoughts are with the victims and their families as we honor their memories one year on from that terrible day in Manchester."

Tributes were also made by the city's two Premier League football clubs, City and United, with Manchester United saying: "Always Remember. Never Forget. Forever Manchester."

Meanwhile, Greater Manchester Police is continuing its investigation into whether suicide bomber Salman Abedi had accomplices or was supported in his attack.

Detectives are continuing to investigate the Manchester bombing as a live murder inquiry, with a sustained team of around 100 police officers on the case.

Assistant Chief Constable Russ Jackson said: "The events of May 22 will forever be etched into the history of Manchester. The attack at the Manchester Arena has had an enormous impact on the families of the 22 individuals murdered and the hundreds more injured and traumatized. Many officers and staff saw and dealt with things that no one should have to deal with."

Salman Abedi's brother Hashem Abedi remains in custody in Libya, with Britain seeking to extradite him back to Britain to stand trial for allegedly helping the plot.

Britain's security services have not given details of potential terror activity so far this year, but in December the head of security service MI5, Andrew Parker told politicians that during 2017 a total of nine terrorist attacks had been prevented in Britain. Five attacks, including the Manchester bombing and others in London, had got through, four related to Islamist terrorism.

Later Tuesday, more than 3,000 singers from local choirs were scheduled to join forces and share the spirit of solidarity at a "Manchester Together -- With One Voice" event, including a choir of people who were at the arena when the blast struck.

At 10.31 p.m. local time, church and city hall bells will ring out from buildings across the city center to mark the moment of the attack. Meanwhile, thousands of people have left messages on 22 "Trees of Hope" close to the scene of the attack.