LONDON (REUTERS) - Just as his old bandmates Take That soared to the top of the British pop charts for the first time in six years, former member Robbie Williams announced that he was releasing a "surprise" new album.

The album, Under the Radar Volume 1, was issued without any advance publicity and made available only through Williams' own website.

"(There are) loads and loads of songs that I've written that I'm incredibly passionate about," Williams said on a video, which also features his pet cat. "I want you to hear them, otherwise they're just going to remain in my computer."

His album will be competing with Take That's new album, III, which also went on sale on Monday. A single from it, These Days, was released ahead of time last week and went straight to the top of the UK Official Charts.

It was Take That's 12th number one and came 21 years after their first chart success. Williams quit the band in 1995 to launch a solo career. He returned to the group in 2010 but local media said he dropped out again in 2012.

He does not perform on III, which does not feature another original member of the band - Jason Orange - who announced he was leaving Take That in September.