Apple has reported the slowest sales ever of its market-leading iPhone, after years of rocketing growth, but the tech giant still posted record quarterly profit. Net income for the quarter ending December 26 was two per cent higher than the same period a year earlier at $18.4 billion, while revenue of $75.9 billion set another record for the company, also edging up two per cent. The results were largely in line with expectations that sales of iPhones - the driver of two-thirds of Apple revenue - had peaked and that the company would need to find new sources of growth. Apple shares have slid 20 per cent since last year on these concerns. But in after-market trade on Tuesday the stock was down a modest 0.7 per cent at $99.30. "Our team delivered Apple's biggest quarter ever, thanks to the world's most innovative products and all-time record sales of iPhone, Apple Watch and Apple TV," chief executive Tim Cook said in an earnings release. "The growth of our services business accelerated during the quarter to produce record results, and our installed base recently crossed a major milestone of one billion active devices." Apple reported that, overall, a billion iPhones, iPads, Macintosh computers, iPod touch devices, Apple TV units, and Apple Watch wearable computers had "engaged" with its services in the past three months. In the fiscal quarter Apple sold 74.8 million iPhones - a record, but only fractionally higher than the 74.5 million in the same period last year and the slowest growth since the lifestyle-altering handsets were introduced in 2007. Revenue in "Greater China" was up 14 per cent for Apple but weaker in the US and Japan. A big question for Apple is whether it can continue to drive sales growth in a sluggish global economy, amid increasing competition from rival smartphone makers. Apple said that it expected revenue in the current quarter to be between $50 billion and $53 billion. That would probably mean a decline from the $58 billion in the same period of 2015. Apple has been diversifying with new offerings in music and is counting on growth from its Apple Watch and accessories. The company reported sales of "other products" - including the smartwatch and Beats music products - was $4.35 billion in the past quarter, but did not break down those figures. Services accounted for $6 billion. Sales of iPads saw a 56 per cent drop in revenues and 25 per cent dip in unit sales as the market for tablet computers cooled.