Samsung promised to appeal against the decision describing it as “a loss for the American consumer”.

“It will lead to fewer choices, less innovation, and potentially higher prices,” the South Korean firm said.

The statement added that it was “unfortunate that patent law can be manipulated to give one company a monopoly over rectangles with rounded corners”.

Apple, however, said it applauded the court “for finding Samsung’s behaviour wilful and for sending a loud and clear message that stealing isn’t right”.

Apple said it intended to seek sales injunctions at a follow-up hearing on 20 September

The two firms account for more than half of global smartphone and tablet computer sales.

The nine-person jury at the federal court in San Jose, California had to consider 700 questions about each side’s claim that its rival had infringed its intellectual property.

It deliberated for less than three days before coming to a unanimous decision, rejecting all of Samsung’s claims and upholding five of Apple’s allegations, including:

• Some of Samsung’s handsets, including its Galaxy S 4G model, infringed Apple’s design patents for the look of its iPhone including the system it uses to display text and icons
• All the disputed Samsung devices had copied Apple’s “bounce-back response”, which makes lists jump back as if yanked by a rubber band
• Several Samsung devices incorporated Apple’s facility allowing users to zoom into text with a tap of a finger

Apple had wanted $2.5bn in damages. Samsung had sought $519m.