HTC said today its May sales more than doubled over last year on soaring demand for its Android-based smartphones.

The company posted revenue of more than $1.4 billion for the month of May, more than double sales of $650 million in May 2010.

So far this year, HTC has racked up $6.4 billion in sales, more than double the $2.6 billion in revenue it posted during the first five months of 2010.

The Taiwan-based handset manufacturer, which provides month-by-month sales figures, did not elaborate on the results in its announcement. The company is expected to release its full second-quarter results in late July, as it has done in previous years.

The majority of HTC’s handsets and tablets run on Google’s wildly popular Android operating system, though the company also makes Brew- and Windows-based devices. HTC’s website currently offers 14 Android smartphones, two Android tablets, eight Windows Mobile phones, five smartphones running Windows Phone 7 and one device using Qualcomm’s Brew MP platform.

Steep competition in the smartphone market from competing Android smartphone manufacturers like Samsung and Motorola has yet to slow HTC’s sales, which have been steadily increasing for the past two years on the popularity of its Android devices.

HTC made Sprint’s first WiMAX smartphone, the HTC Evo, and will launch a 3D version of the device later this month. The company’s second tablet, the HTC Evo View, will hit Sprint at the same time as the Evo 3D, June 24.