Rihanna launched her River Island fashion line in London's Oxford Street yesterday (04.03.13).

The 25-year-old singer - who unveiled her first clothing range for the high street chain during London Fashion Week last month - celebrated the collection officially going on sale with an appearance at River Island's flagship store and thousands of fans turned up for the first chance to buy her designs.

Police had to hold back throngs of fans who arrived at the store hoping to catch a glimpse of the 'Stay' singer with the launch starting an hour later than planned at 10pm GMT.

Rihanna wore her own design, a black floor-length dress with a thigh high split, for the occasion and later changed into a midriff-baring white top paired with stylish double-waisted jeans from her collection for an exclusive after party at London's DSTRKT night club.

A River Island source told BANG Showbiz exclusively that sales projections for the singer's first fashion collection were ''high'' and the company is pleased with the interest that the line has generated thus far.

The 'Diamonds' hitmaker surprised River Island staff by the amount of time she spent working on the collection at the company's London headquarters.

The source said: ''She was there a lot. We were surprised just how much. She really put her time into it. Everything you see is her work.''

Rihanna for River Island is on sale in stores nationwide.