As other parents receive the worst news imaginable, Charlotte Campbell is being tortured by silence.

Her daughter Olivia has not answered her phone since a deadly bomb ripped through the foyer of Manchester Arena where the 15-year-old had just watched one of her favourite pop stars, Ariana Grande, perform.

The 15-year-old schoolgirl was at the concert with her best friend Adam.

Like other parents desperate to find their children in the wake of the blast which has claimed at least 22 lives and injured 59 people, Ms Campbell took to social media to plead for information.

"Anyone seen my daughter Olivia Campbell #manchester," she wrote.

In the photo was her smiling daughter, with flowers in her hair.

"It's the most horrible feeling ever, to know that your daughter's there and you can't find her and you don't know if she's dead or alive," a tearful Ms Campbell told US news network CNN, in tears.

"I don't know how people can do this to innocent children.

"They're both great fans of her [Ariana]. It was a treat for Adam's birthday. And my daughter's been quite poorly lately and Adam asked her to go as a treat for her as well.

"They've done nothing but talk about it, get excited for it, buying new clothes for it, you know like normal teenage children, really.

"They were going to see one of their favourite artists and it's ended in absolute carnage."

Ms Campbell said she last spoke to her daughter about 8.30pm, shortly before Grande took to the stage.

"She was at the concert, she'd just seen the support act and said she was having an amazing time and thanking me for letting her go," Ms Campbell, who lives in Manchester, told BBC Radio 4's Today program.

She said Olivia's friend Adam had been found in hospital, but there was still no sign of her daughter.

"She was with her friend, Adam. Adam was found about half an hour ago - he's in hospital - but Olivia's not been found yet," the mother said.

"I'm at home phoning everybody: hospitals, police, the centres that the children have been put in. Her dad's actually in Manchester looking for her.

"I've got friends looking for her. I've got people I don't even know looking for her, people messaging me, saying we've got her photo, looking for her, we'll get in contact if we see her.

"I'm just hearing nothing. Her phone's dead."

Ms Campbell also shared a photo of her daughter on Facebook saying: "Please share my daughter is still missing with no news on her".

She said social media had been "wonderful" and thanked those who were helping with the search.

Olivia's name began trending on Twitter after her mother's impassioned plea.

Twitter users around the world began sharing her photo and name.

"Missing: Olivia Campbell at the #Manchester bombing. Her mom Charlotte Campbell is looking for her. Please RETWEET," one Twitter user wrote.

Another said: "Olivia Campbell is still missing!! Retweet!!"

A third wrote: "Olivia Campbell is still missing after the Manchester attack, please retweet and help us find her."

Ms Campbell also spoke to television program Good Morning Britain.

"There's no news and I've just got to wait," she said.

Police have confirmed the blast was the act of a lone suicide bomber who detonated an improvised explosive device in the foyer of the arena as scores of teenagers, pre-teens and their parents were leaving the concert.

Chief Constable Ian Hopkins from Greater Manchester Police said the explosion on Monday night was "the most horrific incident we have had to face in Greater Manchester and one that we all hoped we would never see".

"Families and many young people were out to enjoy a concert at Manchester Arena and have lost their lives," he said.

"Our thoughts are with those victims ... and their loved ones. We continue to do all we can to support them."

with PA