Brown is named artist of the year

Brown's No Air was a duet with American Idol winner Jordin Sparks

R&B singer Chris Brown has been named Billboard magazine's artist of the year for the second time.

The 19-year-old also won the accolade in 2006.

Rapper Lil' Wayne, whose hits this year include Lollipop, was the number two artist with Brown's girlfriend Rihanna at three.

Billboard's artist rankings are determined by album sales as well as digital downloads, radio airplay and internet streams.

Rounding out the top five were Alicia Keys and country singer Taylor Swift.

'Unexpected'

Brown has had a successful 2008 with solo hits With You, Forever and No Air, a collaboration with American Idol winner Jordin Sparks.

Last month, he also won three awards at the American Music Awards, including artist of the year.

But the star says he's still not used to all the honours.

"It's bigger than what I can ever imagine. It's unexpected totally, so it's a surprise," he said.

Billboard named Low, by Flo Rida, as the year's top song, followed by Leona Lewis's Bleeding Love.

Rockers Bon Jovi were also named 2008's top touring act in the world, based on data reported to Billboard Boxscore.

More than two million fans attended the 100 sold-out dates on the band's Lost Highway World Tour.