Chinese carmaker Seres has been granted a patent for what it calls an "in-vehicle toilet" that slides under a passenger's seat for visits to the loo while on the road.

The feature is meant to "satisfy users' toilet needs on long journeys, while camping or while staying in the car", engineers wrote in Seres' patent filing in China on 10 April.

Seres, based in the south-west city of Chongqing, has not announced any cars that have toilets and it is uncertain if any will be made.

Chinese electric vehicles have become increasingly packed with unconventional features, like built-in massage seats, karaoke systems and a fridge, to stand out in a highly competitive market.

The patent filing shows Seres' plans for an onboard toilet that slides out from the bottom of a passenger's seat with a push or through voice-activated commands.

The loo will come with a fan and exhaust pipe to channel odours out of the car, according to the filing on China's intellectual property administration seen by the BBC.

Waste is collected in a tank that has to be emptied manually. The toilet also features a rotating heating element that evaporates urine and dries other waste.

When not in use, the toilet is concealed beneath the seat, making full use of the space inside a car without requiring more room.

In-vehicle toilets are rare - mostly found in long-distance coaches - but are not unheard of in cars.

In the 1950s, a special version of a Rolls-Royce Silver Wraith included an in-built television set and a toilet beneath the passenger seat, according to auction house Sotheby's.

Seres, along with its subsidiary brand Aito, are known for making electric sport utility vehicles - larger cars that stand taller off the ground and have more cargo space.

Most of the company's cars are sold in mainland China, though Seres has also expanded to Europe, the Middle East and Africa.

With dozens of competing brands, China's EV market has become heavily saturated leading to a costly price war that has chipped away at companies' profits.

Seres is one of a few Chinese EV companies that have turned a profit, including world-leading BYD.

Many analysts have sounded the alarm that a vast number of Chinese EV firms are at risk of collapse.