Two of China’s largest smartphone makers look to be heading for a courtroom battle after ZTE claimed its cross-town rival in Shenzhen infringed on two of its camera technology patents.

A letter posted on Weibo (a Chinese microblogging site) claims that Huawei’s Honor X2 and P8 (the latter launched last week in London) violated patents in ZTE’s Nubia smartphone lineup. The letter asks Huawei to halt production and sales of the Honor X2 and threatens legal action if no action is taken.

The accusations come on the same day that Huawei released the P8 in China and also as Hong Kong-listed ZTE gears up to launch the Nubia Z9 in early May.

Huawei has responded by saying the camera technologies it uses in the two models is developed in-house and it has applied for multiple patents that are currently pending. It claims the “slow shutter and capture” feature, one of the patents ZTE is threatening to sue Huawei over, is a “basic photographic technology generally known as ‘bulb’. Different manufacturers apply different technologies for taking photos in bulb mode.”

The company said in a statement that it has “never used the patent mentioned in the letter by our competitor’s lawyer, and we therefore contest the allegations made against us. As a company, Huawei has a strong track record of honoring IPR owned by others.”

It certainly won’t be the first legal battle between the two fierce rivals. The mainland’s two largest telecoms equipment manufacturers were involved in 4G patent disputes in Europe back in 2013. Huawei initiated a series of lawsuits against ZTE in a number of European countries in 2011 covering 4G patents. ZTE, which is listed in Hong Kong, filed a countersuit in China.