One Direction star Liam Payne has described Zayn Malik's departure as "the worst" time for the band, but reassured fans it did not mean the end for the group.
The 21-year-old singer posted a heartfelt message on Twitter after the announcement that Malik had left the world's biggest boy band.
Payne said he felt "deeply saddened" but promised there was more to come from the group.
One Direction's Niall Horan has thanked the band's fans for their support following Zayn Malik's departure.
Been a mad few days and your support has been incredible as per usual ! This in turn Spurs us on to make the best music we possibly can
Put on great shows / tours for you guys. You are the best fans in the world and you deserve nothing less from us!
The lads and I arrived in South Africa this morning . We cannot wait to see all you SA fans for the first time and have great shows.
One Direction star Louis Tomlinson has tweeted his thanks to fans for their support after the shock departure of bandmate Zayn Malik.
As the remaining four members vowed to carry on with the global phenomenon that is 1D, Tomlinson said they would work "harder than ever" on their planned fifth album, making it the "best ever".
Been a crazy couple of days but know that we are going to work harder than ever to deliver the best album we've ever made for you guys !
Your support has been incredible , truly incredible so thank you so much !
Harry Styles appeared to break down in tears on stage last night in Jakarta, Indonesia, apparently struggling to come to terms with Zayn Malik's sudden departure from One Direction.
He wiped away tears as the band performed the last leg of their On The Road Again Tour, just hours after the news of Malik's leaving broke.
All the love as always. H
The group said they would continue as a four-piece for the tour and record another album - their fifth - later this year.
A spokesman for the band said Malik, who grew up in Bradford, is at home with his family and fiancee Edwards.
So glad to be in bed after a long and strange 24 hours
The news devastated millions of One Direction's fans around the world, and many took to social media to vent their feelings. Childline have warned that many young people will be feeling severely anxious and distressed by the news, and have urged family members and friends to be gentle and not "undermine" their feelings of distress by dismissing them.
Britain's Culture Secretary Sajid Javid admitted he is an admirer of One Direction's Zayn Malik tonight as he tweeted about how his family had reacted to the news the band member had quit:
X Factor judge Louis Walsh has indicated that the One Direction lifestyle of travelling and touring constantly has meant the band have been living "in a bubble" for the past five years and said "something had to give."
Walsh told Irish radio station RTE Radio One:
"I have heard the rumours for the last few weeks that everything wasn't happy in paradise.
"The problem with these guys is they've been in a bubble for the last five years, pressure, working, a lot harder than people think, so something had to give. So Zayn was the first person just to crack up a little bit.
"He's had an amazing time with the other guys. That's the good side of it. The dark side of it is all the travelling, the airports, in a bubble, not really seeing real life."
Fellow former X-Factor boyband members have tweeted messages of support for Zayn Malik tonight after the One Direction star made the decision to quit the band.
Aston Merrygold, of JLS fame, and Union J's Josh Cuthbert both tweeted the star the "best of luck" following the announcement of his departure:
Counselling service ChildLine have warned that young people may be feeling "very distressed" after hearing the news that Zayn Malik has left boyband One Direction, and urged adults not to "undermine" these feelings.
Sue Minto, head of ChildLine, said: "There are young people who are going to feel seriously distressed at the news, and people are going to have to get their head around the fact that for some this will be very distressing and not to undermine it, even if they don't quite understand it."
She added: "Lots of people have pop stars or celebrities or actors who they hold in high esteem, and there is a lot of sadness and impact for people when something happens to any of them."
Anyone who is feeling distressed can contact ChildLine by calling 0800 11 11 or visit www.childline.org.uk.
Former X Factor judge Gary Barlow and McFly drummer Harry Judd have tweeted messages of support to the remaining members of One Direction, departing band member Zayn Malik, and the band's fans tonight.
The stars tweeted:
Bum out news for 1D fans ? Sad to see Zayn go but you gotta do what you gotta do. Brave decision
Malik, 22, first shot to fame after appearing on the X Factor in 2010, now five years after joining One Direction he is quitting the band.Read the full story ›