MANCHESTER, England (Reuters) - U.S. pop singer Ariana Grande headlined a star-studded benefit concert in Manchester on Sunday that was both joyful and mournful, in aid of victims of the bombing that rocked the city last month, as security fears ran high after attackers in London killed seven people.

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Around 50,000 fans crammed into Old Trafford cricket ground under the watchful eye of hundreds of police, including a significant number of armed officers, a sight that would be unusual under normal circumstances.

The show saw performances from big pop acts from both sides of the Atlantic, including local heroes Take That and Liam Gallagher, along with Pharrell Williams, Katy Perry, Justin Bieber, Little Mix, Coldplay, the Black Eyed Peas, and Grande.

The show was a mix of gaiety and somber reflection - fans could at times be seen jumping for joy, while others, holding banners saying “for our angels”, could be seen wiping away tears. The event began with a moment of silence for the victims of the bombing less than two weeks ago.

“I don’t want to feel or hear or see any fear in this building,” U.S. singer Pharrell Williams told the crowd as he led them in a rendition of his hit single “Happy”. “The only thing we’ll feel here tonight is love, and positivity.”

Fellow singer Miley Cyrus joined the rendition and said: “I’d like to wrap my arms around each and every one of you and thank you ... The most important responsibility we have in this time is to take care of one another.”

During her set, “Part of Me”, singer Katy Perry told the crowd: “love conquers fear and love conquers hate, and this love you choose will give you strength and it’s our greatest power,” before asking the crowd to turn and hug the person next to them.

The somber cause that the concert was being held to benefit was never far from the crowd’s mind. Grande told the audience that her song selection was influenced by the mother of 15-year-old Olivia Campbell, who died in last month’s bombing.

“Sorry” singer Justin Bieber also paid tribute, saying: “I just want to take this moment to honor the people that were lost. We love you so much. To the families, we love you so much.”

Up to 14,000 of those who attended Grande’s May 22 concert, at which a suicide bomber killed 22 children and adults, were given free tickets to attend Sunday’s show, with some persuaded to attend by their affection for the pop star, and despite their very real concerns about security.

“I’m real excited, but real scared,” Shannon Beetham, 14, who was injured in last month’s bombing, told Reuters. “We were there in Manchester (arena) as well, I was hit.”

There were also plenty of upbeat moments, such as when a uniformed police officer was seen holding hands and dancing hand-in-hand with young fans, or when former Oasis front man Liam Gallagher belted out a swaggering version of “Rock ‘n’ Roll Star”.

Grande closed the show by inviting all the other performers on stage to help her sing her 2014 hit “One Last Time”, before she closed with a moving solo version of “Somewhere Over the Rainbow”.

Fans seemed to have forgotten any lingering fears about security towards the end of the evening, with a lively crowd of middle-aged fans singing “Tonight, I’m a rock and roll star” as they made their way out of the stadium.