Image copyright Reuters

Apple has reported a jump in sales in the three months to September, driven by sales of its iPhone.

The tech giant's revenue was $51.5bn (£33.6bn), up 22% compared with the same period last year.

It sold more than 48 million iPhones in the period, which it said were "record fourth quarter sales", although the figure did miss analysts' expectations.

It also reported a net income of $11.1bn for the period, adding that 2015 was its most successful ever year.

"The growth was fuelled by record fourth quarter sales of iPhone, the expanded availability of Apple Watch, and all-time records for Mac sales and revenue from services," the company said.

In China, the biggest market for smartphones, Apple's sales nearly doubled from a year ago to $12.52bn. Apple now has 25 stores in China and is opening a new one every month in a market that supplies about a quarter of sales.

That sales figure is a dip from the prior three-month period, however, when Apple recorded revenues of $13.2bn in China.

For the current quarter, Apple estimates global sales of between $75.5bn and $77.5bn.

Morningstar analyst Brian Colello said the forecast was slightly below market expectations, but investors were expecting a worse outcome, which was why the stock initially rose 3% in after hours trading.

Dave Lee, North America technology reporter, San Francisco

2015 has been Apple's most successful year ever. Revenue is up 22% on 2014, mostly thanks to the continued success of the iPhone.

There are few surprises in these latest results - but a few interesting tidbits caught my eye.

Firstly, chief executive Tim Cook has said that as much as 30% of iPhone buyers are Google Android converts, the highest ever conversion rate.

Secondly, while it still feels like Apple sometimes favours its US customers with new features, it's the international sales that are really giving it gusto: 62% of revenue was generated outside of the US this quarter. China accounts for a huge chunk of that - $12.52bn sales in the past three months, almost double what it took in from the country this time last year.

The iPad is still flagging, but that range will be given a shot in the arm by the upcoming iPad Pro.

Oh, and we still don't know how many Apple Watches were sold in this quarter. Analysts put it at around 3.5 million. Still a tiny product line in Apple's terms, but by far and away the most successful smartwatch on the market.