Amazon last night said its profits in the second quarter jumped 12-fold to $2.5 billion as the online giant saw gains across its range of businesses. 

The stronger-than-expected profit helped lift Amazon shares 1.8% in after-hours trading even though its revenue increase came in short of forecasts, rising 39% to $52.9 billion.

Amazon has grown into one of the world's biggest companies on its global e-commerce operations along with cloud computing, artificial intelligence, video, groceries and other operations. 

Chief executive and founder Jeff Bezos, whose Amazon stake has made him the world's richest person, used the quarterly update to highlight Alexa, the digital assistant that powers Amazon electronics along with cars, appliances and other connected devices.

"We want customers to be able to use Alexa wherever they are," said Bezos.

"There are now tens of thousands of developers across more than 150 countries building new devices using the Alexa Voice Service, and the number of Alexa-enabled devices has more than tripled in the past year," he said. 

Amazon built a reputation for making little or no profit in its early years, but has recently ramped up profitability. 

The profit in the quarter to the end of June compared with net income of $197m the same time last year. 

The latest update showed an operating profit of $1.8 billion for its North American operations, offset in part by an operating loss of $494m in its expanding international segment.

Amazon's large cloud computing segment, which powers systems for business and government clients, delivered an operating profit of $1.6 billion.

The results offered few details on the Whole Foods grocery chain Amazon acquired last year, which has become increasingly integrated into its retail strategy.

At the close of trade yesterday, Amazon's market value was about $877 billion, roughly equal with Google parent Alphabet and trailing Apple at $955 billion.

According to the research firm eMarketer, Amazon's e-commerce revenue will grow more than 28% this year to reach $394 billion, and will account for 49% of US online retail sales and nearly 5% of all retail spending.