Google's sales soared in the fourth quarter as clicks on ads exploded, boosted by mobile searches -- but the amount that advertisers paid Google for those clicks continued to slip. Google also lost money on its Motorola business.

Google said its revenue rose 39% to $11.3 billion in the fourth quarter, excluding advertising sales that it shares with partners.

Net income rose to $2.89 billion, up 6.6% from a year ago.

Shares of Google rose by 5% in afterhours trading.

The number of paid clicks Google racked up surged 24%, but the cost per click fell 6% compared to last year -- the fifth consecutive quarter in which average click costs fell.

Through a search deal with apple, and by activating 1 million android devices a day, Google controls a 93.3% share of the U.S. Mobile search ad market, according to online advertising analysis firm eMarketer.

Though that's a stunning achievement, the entire market is worth less than $2 billion, eMarketer says.