BlackBerry Ltd's unconventional square-screened smartphone, the Passport, earned mixed reviews at its launch on Wednesday as the company's turnaround push moved into a critical phase in which it must prove its handsets are still desirable.

BlackBerry showed off the new device at events in Toronto, London and Dubai. The smartphone, which has a large touchscreen and a modified version of the company's well-known keyboard, comes to market as the phones of BlackBerry's rivals all converge on a tall, rectangular profile.

The Canadian company says its new device is ideal for professionals who need secure access and editing control of spreadsheets, medical scans and other documents. But reviewers said consumers may be disappointed to find some popular apps, including Instagram, were missing at launch.