San Francisco, Feb 1 (IANS): Fuelled by the growth in its Cloud arm, Amazon Web Services (AWS) and advertising business, Amazon's revenue hit $72.4 billion in the fourth quarter that ended December 31 -- up 20 per cent from the same period a year ago.

The strong end to the year pushed Amazon's annual sales to $232.9 billion.

Net income increased to $3 billion in the fourth quarter, compared with $1.9 billion in the fourth quarter of 2017.

AWS saw sales up 45 per cent from the prior year to $7.4 billion. AWS now provides 60 Availability Zones across 20 infrastructure regions globally, with another 12 Availability Zones and four regions coming online by the first half of 2020.

The year brought a defining moment for Amazon's smart home speaker Alexa.

"Alexa was very busy during her holiday season. Echo Dot was the best-selling item across all products on Amazon globally, and customers purchased millions more devices from the Echo family compared to last year," said Jeff Bezos, Amazon Founder and CEO.

Customers can now choose from more than 28,000 Alexa-compatible smart home devices from more than 4,500 unique brands.

"In 2018, we improved Alexa's ability to understand requests and answer questions by more than 20 per cent through advances in machine learning," Bezos added.

Developers doubled the number of Alexa skills to over 80,000, and customers spoke to Alexa tens of billions more times in 2018.

The all-new Echo Dot was the top selling product on Amazon globally.

Device makers announced more new Alexa products,, including the Lenovo Smart Tab and new devices from brands like First Alert, Jabra, JBL, Kohler, LG, and Razer.

Amazon partnered with ICICI Bank to launch the Amazon ICICI Bank credit card to pre-selected customers in India.

"This is the first card in the country to offer Prime members 5 per cent in reward points for their purchases on Amazon.in and reward points for all other payments where Visa is accepted," said the company.