Washington: Google CEO Sundar Pichai has backed Apple in its battle with FBI over opposing a US court's ruling to unlock the iPhone of a Pakistani-American terrorist who shot dead 14 people in California, saying forcing companies to enable hacking could "compromise" user's privacy.

In a series of tweets, Pichai said that although Google gives "law enforcement access to data based on valid legal orders", but it is "wholly different than requiring companies to enable hacking of customer devices and data," which could set a "troubling precendent".