Apple appeared in a Shanghai court on Wednesday, accused by a Chinese firm of copying software used for the "Siri" personal assistant on its hugely popular iPhones.
The Californian company's products are big sellers in China, and chief executive Tim Cook said in January he expects it to surpass the US as the firm's largest market, but the relationship is sometimes troubled.
Shanghai's Zhizhen Network Technology Co. claims Apple infringed its patent for voice recognition software, and the two companies were summoned to present evidence at a pre-trial hearing, representatives of the Chinese firm said.
The legal challenge comes after Apple last year paid $60 million to Chinese computer maker Shenzhen Proview Technology to settle a long-running dispute over the "iPad" trademark, whose ownership was claimed by both companies.
State media have also attacked Apple in recent days, with the People's Daily urging consumers in a commentary to "strike away Apple's unparalleled arrogance" for alleged double standards in customer service and returns policies.
Apple has denied those accusations in statements to Chinese media.
Zhizhen says it patented its "Xiao i Robot" software in 2004, while Apple's Siri, which made its debut with the release of the iPhone 4S in 2011, was first developed in 2007.
Siri, described by Apple as an "intelligent personal assistant", responds to a user's commands through voice recognition software.
The Chinese company's product operates in a similar way and works on Apple's iOS system as well as rival Android.
It has wide application in areas including telecommunications, finance and e-commerce and Zhizhen claims more than 100 million users in China, according to a statement.
"The company will ask Apple to stop manufacturing and selling products using its patent rights, once Apple's infringement is confirmed," Si Weijiang, a lawyer representing Zhizhen, told AFP.
"We don't exclude the possibility of demanding compensation in the future," he said.
In court Apple denied the allegations and unsuccessfully asked for the case to be rejected, he added.
Apple did not respond to requests for comment.
The full case is scheduled to be heard in July, Zhizhen spokeswoman Mei Li told AFP.
"We surely have confidence, our lawyers also told us they have confidence, but of course we will have to see how the judge will rule," she said.
Explore further: Google hits back at rivals with futuristic HQ plan