The expansion of government surveillance efforts in China and the role that US tech firms played in it - was the foundation of investigative stories from The Associated Press that won a Pulitzer Prize Monday for international reporting.

The Pulitzer board recognised AP journalists Dake Kang, Garance Burke, Byron Tau and Aniruddha Ghosal, along with contributor and independent journalist Yael Grauer, for what it called "an astonishing global investigation into state-of-the-art tools of mass surveillance" that also included a story about the expansion of license plate surveillance of drivers in the United States by the US Border Patrol.