A Chinese company suing Apple over similarities between its product and the "Siri" personal assistant believes its case has merit and is awaiting a court ruling, a lawyer said Tuesday.

Shanghai's Zhizhen Network Technology, which holds the rights to "Xiao i Robot" software patented in 2004, has accused the US technology giant of infringing patents with its "intelligent personal assistant" Siri.

The case was formally heard by a Shanghai court in July last year but no ruling has been announced.

"We think we'll win the case," Yuan Yang, a lawyer for Zhizhen, told AFP. "We hope to make things clear and let the court judge according to the law and give the Chinese patent holder the reward it deserves."

Separately, Apple is seeking a judicial review of the Chinese company's original rights over "Xiao i Robot", Zhizhen said.

The firm said in a statement that an Apple subsidiary had sought to have Zhizhen's patent declared invalid by China's patent review board, which operates under the government's State Intellectual Property Office.

It said the board upheld Zhizhen's patent in September last year. Apple was seeking a judicial review of the decision, which would be heard by a Beijing court on Thursday.

"Under normal circumstances, it should be rejected," lawyer Yuan said. "We're still optimistic. We trust the court will make an impartial judgement."

Apple and the patent review board declined to comment. An official of the State Intellectual Property Office also declined comment, but said such appeals were common.

China's official Xinhua news agency on Monday described the case as a lawsuit.

Siri, which responds to a user's commands through voice recognition software, made its formal debut with the release of the iPhone 4S in 2011.

Zhizhen claims its product works in a similar way and has wide applications in areas including telecommunications, finance and e-commerce.