Could've been imported for testing by local suppliers.
Carwale has acquired photographs of an undisguised Perodua Axia in Mumbai with Malaysian number plates, which does bring up quite a few questions.
It's not uncommon to see cars from manufacturers not established in the Indian market plying on Indian roads. Most cars are imported by local suppliers or rival manufacturers for benchmark or component testing, so it's likely that the Perodua Axia was imported for such purposes.
However, the Axia shares its platform and components with the Daihatsu Ayla, a hatchback from a manufacturer that has been in the news recently for plotting an entry into India. So another reason could be engineers tuning the platform and components to better suit Indian driving conditions, although it does seem a bit early as the Daihatsu brand is reported to arrive in 2-3 years from now. Another possibility is that this could belong to the Malaysian Embassy in Mumbai, hence the Malaysian number plates.
The Axia's performance figures match that of top entry-level hatchbacks like the Maruti Celerio, WagonR, and the Tata Tiago. It is powered by a 998 cc Toyota-sourced petrol engine that produces 66 hp and a peak torque of 90 Nm. It can be had with a 5-speed manual and a 4-speed automatic.