(Yicai Global) June 28 -- As hot summer days reign, the patent war between China's major air-conditioner manufacturers, GD Midea Air-Conditioning Equipment Co. and Gree Electric Appliances, gathers momentum.

Midea filed three patent infringement lawsuits against Gree last week, Yicai Global reporter learned, including one invention patent and two utility model patents, claiming CNY40 million (USD5.8 million) in compensation.

The move is seen by market observers as Midea's counterattack against Gree's recent filing of patent lawsuits against Midea. Gree sued Midea and its sales company for infringing its utility model patent in one of Midea's air conditioner series named "Cooling King," and claimed CNY50 million in compensation, a case accepted by The Beijing Intellectual Property Court.

It is not the first patent infringement litigation between the two parties. There were mixed results during several lawsuits both companies launched against one another between 2008 and 2013. Unlike previous practice, Midea actively fights back this time.

A senior executive of Midea told Yicai Global that instead of a design patent, a patent for invention was infringed in its compressor technology. "Most of household appliance manufacturers infringed our patent and someone inside our company proposed in 2016 to file a lawsuit, but we didn't do so because it was unnecessary to offend the whole industry. However, as Gree has sued us, we will certainly fight back," he said.

An analyst for the household appliance industry said both parties should calm down to avoid having an adverse impact on the whole industry. Zhang Yanbin, vice president and director of Air Conditioner Industry Research Institute at avc-mr.com, told Yicai Global that this means that Chinese household appliance manufacturers choose to take legal actions as a way of competing each other in addition to usual market means.