Google's second-quarter profits rose by less than expected, fuelling concerns of a slowdown in the online advertising sector.

The US internet search giant reported a profit of $1.25bn between April and June, down from $1.31bn in the same quarter a year earlier.

The results were just below market forecasts, and in after-hours trade on Wall Street, Google shares fell 8 per cent.

Canaccord Adams analyst Colin Gillis told the BBC: "There's the initial shock of this being the best company in the space and it just fell short."

California-based Google also announced a 39 per cent yearly hike in revenue totaling $5.37bn and earnings-per-share of $3.92 on 318 million diluted shares outstanding.

Eric Schmidt, chief executive of Google, described the firm's performance as "another strong quarter, despite a more "challenging economic environment".