Apple is tight-lipped about its upcoming devices dubbed as iPhone 6s and iPhone 6s Plus. Several expected features have been leaked over the last few weeks with the release date drawing close.

It was earlier reported that the Cupertino-based giant will unveil the models on 11 September before opening for advance booking on 18, but the company has now revealed that it will hold an event on 9 September in San Francisco, giving a hint that the devices could be announced on the day.

Mac4ever (via PhoneArena) had earlier reported that iPhone 6s and iPhone 6s Plus will be up for pre-orders on 11 September before shipments kick off on 18 September, while Telegraph and New Phone claimed that the devices will be opened for advance booking on 18 September and released on 25.

Apple is expected to reveal the features of the upcoming devices only on the day of the launch but several leaks have exposed some key features. Here are some of the killer features expected in the devices:

Display: Both iPhone 6s and iPhone 6s Plus are expected to have similar features except the screen size. The former is expected to be 7 mm thick (6.9 mm thick in the iPhone 6) and the latter 7.13 mm thick (7.1 mm thick in the iPhone 6 Plus), according to a report by M.I.C. Gadget. It is reported that iPhone 6s will sport a 4.7-inch display and 6s Plus will have a 5.5-inch screen.

Processor: The upcoming devices are expected to be powered by an A9 chip processor. Its predecessors, the iPhone 6 and iPhone 6 Plus come with A8 chip.

Operating System: The iPhone 6s and iPhone 6s Plus are most likely to run on the upcoming firmware, iOS 9.

Camera: The iPhone 6 and iPhone 6 Plus house an 8 MP rear camera and a 1.2 MP secondary snapper, which is inferior to its rivals as far as megapixel is concerned, and for which they were criticised. Now, it is reported that the upcoming Apple devices will have a 12 MP main camera.

Force Touch: It is reported Apple's new devices will have Force Touch feature seen in MacBook and Apple Watch.

Build Quality: iPhone 6 and 6 Plus were hit hard by "bendgate" issue, so the upcoming devices are expected to come with a stronger build. It may come with stronger aluminium alloy chassis.