A high-performance Lexus GS-F appears well on its way, with a development prototype spied undergoing engineering work.

Lexus GS-F - 1

The spy shots of the BMW M5-hunting Lexus GS-F show the Japanese car maker's determination to challenge its German rivals, coming two weeks after our spy photographers snapped the M4-rivalling Lexus IS-F Coupe.

While apparently yet to leave the garage, the Lexus GS-F prototype differentiates itself from the standard GS sedan with a quad-tipped, stacked exhaust, rear diffuser and a boot lip spoiler.

Lexus GS-F - 2

The multi-spoke alloy wheels wrapped in high-performance rubber also match those seen on the spied IS-F Coupe. The car has also been de-badged.

Our spy photographers tell us that each time the garage door was opened, giving a view of the GS-F prototype, the Lexus engineers working on the performance sedan would try to block the view.

With details yet to be confirmed, the Lexus GS-F is sure to be lighter than the current 3.5-litre V6-engined 1870kg GS and be more powerful than the existing 311kW/505Nm 5.0-litre V8-powered Lexus IS-F sedan.

Lexus GS-F - 4

Landing in local showrooms in September, the freshly updated BMW M5 now comes standard with the performance-boosting Competition Package, resulting in its 4.4-litre twin-turbocharged V8 putting out 423kW and 680Nm.

Early speculation suggests the Lexus GS-F could be seen as early as next year.