New Delhi: After media reports surfaced last week that Chinese smartphone makers Xiaomi and Coolpad have locked horns over patents, the latter on Monday confirmed that it has sued three group firms of Xiaomi for several patent infringements.

Coolpad subsidiary Yulong that filed the fresh suit, demanded that Xiaomi should immediately stop production, offerings on sale and current sale of smatphones, including Xiaomi 6, Xiaomi Max2, Xiaomi Note3, Xiaomi 5X, Redmi Note4X and Mi MIX2 -- some of which are high-selling models in India.

Coolpad has alleged that Xiaomi violated its patented multi-SIM card design and other technology related to user interface.

Yulong Computer Telecommunication Scientific (Shenzhen) Co. Limited filed the lawsuit against Xiaomi Telecom Technology Co, Xiaomi Technology Co and Xiaomi Factory Co, in a Jiangsu court in China for using its patents without authorisation, a statement said.

The lawsuit comes at a time when Xiaomi has officially filed for an IPO in Hong Kong that aims to raise $10 billion in a sale that may value the company at $100 billion.

"It's very important to safegaurd your inventions and make sure no one use them for any commercial purpose without permission.

"As we already have over 13,000 patent applications globally and out of them 2,000 has been already authorised, we are looking forward to do whatever it needs to make sure they are not infringed upon," said Syed Tajuddin, CEO, Coolpad India.

"We are still working in a very cooperative manner to workout best possible solutions to resolve this case with Xioami," he added.

Yulong had filed a similar legal case against Xiaomi in a Shenzhen court in January.

The patents involved in the lawsuit are systematic interactions or user interface (UI) type patents. They involve basic communication, display and interactive functions of mobile phones, and are difficult to circumvented or replaced.

"Since 2014, Coolpad has repeatedly sent warning letters to Xiaomi, stating that the mobile phone it sold was suspected of infringing on Coolpad's patent rights and proposed friendly negotiation, but did not receive a response.

"In desperation, Coolpad could only seek redress through legal channels," said Nancy Zhang, Coolpad's Global Chief Patent Officer.

"If cumulative achievements of thousands of R&D engineers' working from day to night for 25 years, are arbitrarily plagiarised and not pursued, we should reflect on our tolerance and this will ultimately harm innovation in the entire nation and the future generations," warned Coolpad Group CEO Jiang Chao.

At $10 billion, Xiaomi's IPO would also be the 15th biggest of all time, or the fourth-largest in Hong Kong.

According to the regulatory filing with the Hong Kong stock exchange, Xiaomi also reported a revenue of $18 billion and a gross profit of $2.3 billion in 2017.

The company is currently at the fourth position in the smartphone market globally, behind Samsung, Apple and Huawei.