After infiltrating Gemalto, both the NSA and GCHQ began monitoring calls and data transfers on mobile communication devices across the globe.
The latest data available for the year 2010 shows that China bought 45 percent of the chipmaker's SIM cards, accounting for nearly half of Gemalto's global sales.
The Amsterdam-based company entered the Chinese market in the 1990s.
Among Gemalto's partners are the country's biggest mobile telecommunication companies China Mobile, China Unicom and China Telecom.
"We take this publication very seriously and will devote all resources necessary to fully investigate and understand the scope of such sophisticated techniques," Gemalto said.
On Thursday, Executive Vice President Paul Beverly told The Intercept, the publication that broke the story, the implications and sources of the attack have not been determined yet.
The latest revelations are part of 1.7 million classified documents leaked in 2013 by former NSA contractor Edward Snowden, causing a US mass surveillance scandal.
