The Spice Girls - Britain's all-girl band phenomenon of the 1990s - Thursday announced their long-awaited reunion and said they were planning a new album and a world tour later this year.

The group, which includes Victoria Beckham, made the comeback announcement at a news conference in London, saying it was their way of "saying thank you" to their fans.

Beckham (Posh Spice), Geri Halliwell (Ginger Spice), Mel Brown (Scary Spice), Mel Chisholm (Sporty Spice) and Emma Bunton (Baby Spice) first exploded on to the pop scene in the mid-1990s with their first single, Wannabe.

The "girl power" band, which split up in 2001, has sold more than 55 million records. They are in their 30s now.

Geri Halliwell, who prompted the split by walking out in 1998, confirmed that the reunion is not going to be for good.

"This is going to be a one-night stand," she said.

Mel C, who had vowed "never" to take part in a reunion, said: "A girl's allowed to change her mind."

The girls promised to sing all their classical hits during the 11-dates tour of six continents, kicking off in Los Angeles on December 7.

After Las Vegas and New York, they will stage concerts in London, Cologne, Madrid, Beijing, Hong Kong, Sydney, Cape Town and Buenos Aires.

A greatest hits album would be released before Christmas, they announced.

At the height of their 1990s success, the group exercised their "girl power" by replacing their manager and signing up with Simon Fuller, the famous pop manager who has masterminded their comeback.

"Wannabe", released in 1996, became the biggest-selling single by an all-female group. It was followed by a string of number ones, with songs like "Say You'll Be There", and "2 Become 1".

Their debut album, "Spice", made them the fastest-selling British act since the Beatles, and the band - particularly Geri Halliwell's Union flag dress - epitomised "Cool Britannia" in the aftermath of Labour's 1997 election victory.