Microsoft's cloud computing platform Azure has broken the $1 billion annual sales mark, the company had told news agency Bloomberg. 

The figure includes direct sales of Azure, as well as "software provided to partners to create related Windows cloud services", Bloomberg said. 

The revelation comes soon after Microsoft claimed that Office 365 – the cloud-hosted version of its desktop productivity suite – is selling at annualised run rate of $1 billion. 

Amazon.com does not report the size of its cloud business, Amazon Web Services, so it is not possible to do a precise comparison. In January, an analyst from investment bank Macquarie Capital estimated that AWS took in sales of $2.1 billion in 2012, and will reach $3.8 billion in 2013. 

If true, that means Salesforce.com is still the world's largest cloud provider, with 2012 revenue of $2.3 billion. 

Until this month, Microsoft's Azure offered only a "platform as a service" (PaaS) option, meaning that customers had to use the Windows platform to build applications. However, two weeks ago it announced the general availability of its "infrastructure as a service" (IaaS) offering, which allows customer to provision raw servers and storage.