Tech giant Apple posted a surprise drop in sales of its flagship device in its fiscal second quarter, in an apparent sign that customers are eagerly waiting for its 10th-anniversary iPhone this September, which is rumoured to have a curved or bezel-less display, 3D facial recognition and wireless charging.

The world's most valuable company by market capitalisation reported that it sold 50.76 million iPhones in the three-month period ended April 1, marginally down one per cent from 51.19 million a year earlier, according to figures released at around 12:30am Dubai time on Wednesday.

Revenue, however, rose five per cent from last first quarter's $50.56 billion to $52.9 billion, not far from forecasts of $53.02 billion, helped by an 18 per cent leap in its Services area - which include the App Store, Apple Music, iCloud and Apple Pay - from last year's $5.99 billion to $7.04 billion.

Its Other Products category - which includes the Apple Watch, AirPods and Beats products - also provided a lift, up at $2.87 billion, 31 per cent better than the year-ago's $2.19 billion.

iPad sales, meanwhile, dropped 12 per cent year-on-year from $4.41 billion to $3.89 billion year-on-year, while Macs jumped 14 per cent from $5.11 billion to $5.84 billion.

"We are proud to report a strong March quarter, with revenue growth accelerating from the December quarter and continued robust demand for the iPhone 7," Apple CEO Tim Cook said in a statement.

He added that the iPhone Product(RED) had seen "great customer demand", and highlighted that Apple's Services business posted its highest revenue ever for a 13-week quarter.