Liam Payne says this last week has been the ''worst time'' for One Direction.

The 21-year-old singer has said him and the rest of the band - Harry Styles, Louis Tomlinson and Niall Horan - are ''deeply saddened'' by the departure of Zayn Malik, who announced he was leaving the group yesterday (25.03.15).

Writing on Twitter, he said: ''This last week has been some of the worst times, possibly the worst it's something we are all deeply saddened by.

''It's sad to think for the time being we won't grace the stage as five bros or have the same fun on a tour bus or laughs in a hotel together that we have over the years but I'm super sure us and zayn will always remain the closest friends. (sic)''

And the 'Night Changes' hitmaker has promised it's ''far from over'' for the four singers as they continue their world tour.

He added: ''I guess what I'm really trying to say is it's far from over. When we very 1st became successful we all agreed that one direction had become much bigger than each individual member that's why I feel like right now it's ok to be sad and upset but I do ask everyone who is a fan of us to please keep ur faith in us I'm sure there's a lot more to come (sic)''

Liam also admitted he is still trying to ''understand'' the band's worldwide success.

He shared: ''For the past five years now I've been part of something so special I don't think any of us really understand, something that can mean the world to people and put a smile on the face of our fans even in the darkest times.

''To a lot of people it's just a bunch of silly kids in a band but to the people involved it means so much more. (sic)''