Muscled out of the smartphone market by iPhone, Android and Samsung - BlackBerry has rolled the dice on its latest product and come up with a square phone.

The Canadian firm has unveiled more details about the unusual device called the Passport, which it first previewed in June, including a 4.5-inch square HD screen.

A post on the official BlackBerry blog said "Many have thought that creativity around the design of smartphones was dead. Device companies have been emulating the same, entertainment-driven look for so long that there's been a homogenisation of the visual cues in smartphone design".

The screen width fits 60 characters rather than the 40 seen on a rectangular five-inch device.

Under the heading "it's hip to be square", the post said the width is ideal for reading ebooks, viewing documents and browsing the web.

Comparing it to a giant cinema screen, the post added "The Passport is like the IMAX of productivity and you don't have to sacrifice screen real estate, vertically or horizontally".

The post said the device was aimed at professionals such as architects, writers and medical staff.

Earlier this year, BlackBerry announced a quarterly loss of €310 million (US$423m) after suffering a revenue drop of more than 60%.

The company said its revenue for the last quarter of 2013 was €715.5 million (US$976m), down from €1.97 billion (US$2.7bn) in the previous year.

It was the first time the Canadian company had reported quarterly revenue of below US$1 billion. The figure was more than a tenth lower than what analysts had forecast.

Early last year, the company released BlackBerry 10, which failed to spark a turnaround in its fortunes.