London-based Symbian announced today at 3GSM that it shipped 51.7 million Symbian smartphones to consumers worldwide in 2006, keeping it the clear leader in the high-end operating system phone market.

Compared with the previous year, Symbian shipped 52 percent more phones in 2006.

Symbian develops operating system for advanced mobile phones, and is primarily used by Nokia, which is part owner of the company. The company is also owned by Ericsson, Panasonic, Samsung, Siemens and Sony Ericsson.

Microsoft officially unveiled the latest version -- Windows Mobile 6 -- of its operating system on Monday, after the news was leaked last week. Scott Horn, director of marketing for Microsoft's mobile and embedded-devices group, said the software giant is catching up.

Horn said Microsoft shipped its operating system on 6 million devices in its last fiscal year. That represents a 90 percent increase for Windows-based phones year over year.