A unit of China’s leading genetic testing company BGI Group filed a patent infringement case against U.S. genomics giant Illumina Inc. in an escalation of patent disputes surrounding key DNA sequencing technologies.

BGI’s gene sequencing manufacturing subsidiary MGI Tech Co. said Wednesday that its U.S.-based unit Complete Genomics filed the case in Delaware demanding that Illumina immediately stop selling several sequencing products and related sequencing chemistry reagents that allegedly violate BGI patents.

The latest development reflected a heated patent battle between the two genomics companies. Illumina filed two lawsuits in March and May in Europe accusing BGI of patent infringement.

In a statement to Caixin last week, BGI said it “will take corresponding legal actions” to deal with the legal disputes with Illumina and “will not rule out the use of legal weapons such as counterclaims to protect its legal rights.”

In a letter to Caixin, Illumina called the BGI's claims “meritless” and said it "fully expects to succeed in the litigation".