Nanya said on Tuesday it has filed a patent infringement complaint in the U.S. against Japan's Elpida, further escalating the legal battle between the two DRAM makers.

Nanya's complaint, which was filed with the U.S. International Trade Commission (ITC), alleges that Elpida infringed on four of the company's U.S. patents. It requests that the ITC ban the sale and import of Elpida's DRAM products to the U.S.

Nanya's complaint also asks the ITC to investigate Kingston Technology, a California-based chip distributor that has invested in Elpida in the past.

The complaint was filed just a week after Elpida took a similar action against Nanya in the U.S. The complaint requested that the ITC stop imports of Nanya's products in the U.S., claiming that they violated seven of Elpida's patents. Elpida also filed a suit with the Taiwan Intellectual Property Court to stop sales and production of related Nanya products.

Elpida said on Tuesday it does not comment on pending lawsuits.

Nanya said in a statement that the company may also file a patent infringement lawsuit in a U.S. district court.