Best-selling boy band One Direction bounded onto the stage in Johannesburg Saturday for their first show since fans across the world were plunged into teenage distress over heartthrob Zayn Malik quitting the group.

A deafening wall of excited screams greeted the remaining four members of the British-Irish group, who have earned a global following since bursting onto the scene in a television talent show in 2010.

Adoring young fans said they feared the departure of Malik, 22, could mean the break-up of One Direction, but the performers made no mention of their missing bandmate as they tore into a string of hits, including "What Makes You Beautiful".

"Thank you for choosing to spend your evening with us," singer and songwriter Harry Styles told a packed-out Soccer City stadium in the South African city, to loud cheers from the crowd.

"You have no idea how much we love you right now," he said at the start of the energetic set.

Directioners -- as the band's loyal followers are known -- poured into the stadium five hours before their heroes started their set, and many expressed their shock over Malik's departure.

"When my cousin told me, I screamed, and my dad came running down the stairs as he thought that something happened," said Aditi Ramdhani, 13, who had travelled six hours from Durban with her family to see the concert.

"I was heartbroken. He was the quiet one and the most handsome one.

"He has made his decision and I want him to be happy, but it is so sad."

'Our hearts dropped'

Nazeema Ajodha and her daughter Ria booked tickets to see the group play on Saturday night and again on Sunday at the same venue, but said they were distraught not to catch the full line-up.

"When we heard the news, our hearts just dropped," Ria said.

"The band is never going to be the same. Zayn was the one who did all the high notes. He was the best. He was the highlight."

The devotion of 1D's vocal young fans has often been compared to the mania surrounding earlier all-male pop groups like Take That or even the Beatles.

Reports spread of girls threatening to self-harm as news of Malik's exit took over social media, and mental health charities inBritain urged upset fans to seek support.

Among the many dutiful parents in the crowd on Saturday was Anke Gutknecht, who said she had bought tickets 11 months ago for a group of eight family and friends.

"He should have made a go of it and kept together," she said.

"They're young. They've got everything going for them, so I think it was a silly move, but we don't know what the reasons are."

Malik, who flew home from the band's world tour last week suffering from stress, released a statement on Wednesday announcing he had left the band.

"I am leaving because I want to be a normal 22-year-old," he said.

Oratile Mokubyane, who took his 10-year-old sister to the concert, said she was tearful at Malik's leaving.

"Our house is covered in One Direction stuff," he said. "She is threatening to cross his head out of all her photographs."

One Direction heads to Europe next before a string of concerts across the United States.