Microsoft has accidentally put the long-rumored Lumia 950 and 950 XL on its UK Windows 10 phone store, ruining one of the biggest announcements set for the company's October 6 event.

The listing states the 950 will have a 5.2-inch WQHD display, a 20 megapixel camera with Zeiss optics, 32GB storage with up to 2TB expansion via microSD. The 950 XL, meanwhile, will come with a 5.7-inch display at same resolution, same camera and storage options. The listing is missing a price.

lumia 950 The Lumia 950 and 950 XL as they appear on Microsoft's website. Photo: Microsoft.com

The slip-up is a major error for Microsoft, as it tries to keep as much as possibly under wraps about its upcoming event. Other rumored announcements include a Surface Pro 4 and Microsoft Band 2. The company appears to have chosen not to list those online.

Other leaks have revealed the 950 will come with a Snapdragon 808 processor and 3000mAh battery, while the larger 950 XL will include a Snapdragon 810 and 3300mAh battery. Both devices are said to include 3GB of RAM, a 5 megapixel front-facing camera and wireless charging. The devices will also take advantage of new Windows 10 features: iris scanning will unlock the phone automatically, while a Continuum docking station will let the phone scale up for desktop use with a keyboard and mouse.

The handsets are expected to cost $600 for the 950 and $650 for the 950 XL, placing it at the higher-end of the smartphone market. According to the company's fourth quarter 2015 earnings, the Windows Phone divison is struggling. The company needs the Lumia 950 to be a success, to prove that Windows Phone has potential as a platform for future development.