Twitter reported a disappointing 7 per cent slide in a key measure of engagement by its users in the third quarter, triggering a selloff of more than 9 per cent in its stock last night.

Some investors had raised fears about declining Twitter usage as other social media and mobile messaging services become more popular. Yesterday, the online messaging service also projected fourth-quarter revenue that may miss Wall Street's heightened expectations.

The company reported monthly active users rose 23 per cent to 284 million in the quarter, meeting expectations on an important metric scrutinized by investors, who worry that Twitter’s growth has peaked. That followed 24 per cent

growth in the second quarter.

But timeline views per user, which measures engagement, slid 7 per cent globally to 636. Views slid 6 percent in the United States to 774. And overall, total timeline views of 181 billion slightly missed analysts' expectations.

Yesterday, the messaging service said revenue more than doubled to $361 million in the third quarter, beating an average forecast for $351.4 million. But it projected sales of $440 million to $450 million in the holiday quarter, versus expectations for around $448.8 million.

Shares in the company slid 9.1 per cent to $44.17 in after hours trading, after closing at $48.56 on the New York Stock Exchange.