Samsung has announced that its Galaxy S4 smartphone has sold more than 40 million units to date, Digital Spy said.

The flagship handset shifted an additional 10 million units in the last two months to reach the milestone six months on from its launch.

The figures indicate that the device has outperformed its predecessor, with the Galaxy S3 taking seven months to surpass 40 million sales.

However, Samsung is said to be dissatisfied with the Galaxy S4's market performance, as the South Korean company was believed to have been targeting more than 40 million sales by this point.

Recent reports suggest that the firm is fast-tracking the Galaxy S5 to market in a bid to challenge Apple's iPhone 5S, targeting a potential January 2014 launch for the device.

Samsung recently announced its quarterly financial results reporting 10.1 trillion won (£5.9 bn / $9.5 bn) in operating profit, up from 8.06 trillion won (£4.7 bn / $7.6 bn) this time last year.