One Direction star Liam Payne appears to be heartbroken after the singer tweeted a series of cryptic messages on Twitter.

The tweets have fuelled speculation that he has split from girlfriend Sophia Smith.

The 20-year-old singer, who has been in a relationship with Smith for nine months, appeared to be expressing his sadness at a break-up.

Tweeting in the early hours of the morning following the band's concert in Santiago, Chile, he wrote: "Can't be without you ... Worse thing I ever did was let you go... No (sic) all I got left is the thought of you."

The couple, who went to school together at St. Peter's Collegiate School in Wolverhampton, went public with their relationship last August.

Months earlier Payne had split from long-term girlfriend Danielle Peazer, 25, a dancer who he had met on the X Factor in 2010.

Smith was spotted at the One Direction concert in Los Angeles, where she was sitting in the audience with the singer's parents, Geoff and Karen, and his two sisters, Ruth and Nicola.

The couple were last photographed together at a book launch in London just over five weeks ago.

With One Direction kicking off their seven month long world tour last week, the couple would inevitably be spending long periods of time apart.

The Where We Are tour kicked off on April 25 in Colombia and is due to finish in October after taking in 69 dates across South and North America and Europe.

The band are due to travel to Argentina this weekend ahead of their gig in Buenos Aires on Saturday.