Twitter says that four executives are leaving the company.

Its stock fell more than 4 per cent in premarket trading.

CEO Jack Dorsey posted a statement to the microblogging service saying that Alex Roetter, Skip Schipper, Katie Stanton and Kevin Weil are exiting the company. Dorsey said he wanted to address employees later this week, but issued a statement due to `inaccurate press rumors' about the departures.

Roetter served as senior vice president of engineering, Schipper was vice president of human resources, Stanton was vice president of social media and Weil was senior vice president of product.

Dorsey said that chief operating officer Adam Bain would be taking on some additional responsibilities on an interim basis. Chief technology officer Adam Messinger will also be assuming some responsibilities.

After a long streak of robust growth that turned it into one of the internet's hottest companies, Twitter's growth has slowed dramatically during the past year-and-half to leave the San Francisco-based company scrambling to catch up with social networking leader Facebook and its 1.5 billion users.

Twitter Inc.'s malaise resulted in the departure of Dick Costolo as the company's CEO last July and ushered in the return of Dorsey, who had been ousted as the company's leader in 2008.

Dorsey helped invent Twitter in 2006 and imposed a 140-character limit on messages so the service would be easy to use on cellphones that had 160-character limits on texts at that time. Those texting limits on phones faded away several years ago as the advent of smartphones enabled people to use other Internet messaging services. Twitter may be looking to expand beyond its 140 character tweets in a bid to make its service more appealing to wider audience.

​Neil Bearse, marketing professor with the Smith School of Business at Queen's University, said the move is not surprising given Twitter's stalled trajectory.

"Hard to know what the true story is, but I think you see a company [where] user growth has really stalled, their ability to ship product has really stalled last couple of years. They've got a new leader in place and that potentially means it's time to clean house," he told CBC News.

He said the company has to show Wall Street it can take a new direction and really innovate.

"Twitter's next move has to be the announcement of new advisers to their board. They have to tell a positive story," he said.

The decision to allow to longer posts may be a way forward, he added.

"The best way to do innovation is to look at what your customers want," Bearse said.