Internet search provider Google has reported higher revenue and profit for the fourth quarter, but its revenues have fallen short of analysts' estimates due to lower online ad prices and a strong US dollar.

The company reported fourth-quarter profits of $4.76bn (£3.16bn, €4.2bn), up about 30% from the same period last year. Its total revenue increased by 15% to $18bn.

Excluding payments to Google's advertising partners, revenue was $14.5bn, below analysts' estimates of $14.8bn, according to Bloomberg.

Google's advertising revenues were hit by consumers' increased use of the internet on mobile devices, on which ad rates are lower. During the fourth quarter, the company's average price of online ads or "cost per click" was 3% lower than last year, despite a 14% increase in consumer clicks.

Google did not reveal the amount of revenue it earned from mobile devices.

The company was also hit by the recent strength of the US dollar, as it generates most of its revenue overseas. Google noted that its revenue would have been $541m higher if foreign exchange rates were more favourable.

In addition, the company's growing operating expenses affected its profitability significantly. The company's operating profit margin for the fourth quarter was 24%, down from 28% in the same quarter last year.

Google has increased its staff count by about 5,000 over the past six months to a total of 53,600. Research and development costs increased 45%, to $2.8bn, while capital expenditures rose to a record $3.6bn.