Apple has posted the biggest quarterly profit ever made by a public company.

The giant tech reported a net profit of $18 billion in its fiscal first quarter, which tops the $15.9 billion made by ExxonMobil in Q2 2012, according to Standard and Poor’s.

Record sales of iPhones were behind the surge in profits.

Apple sold 74.5 million iPhones in the three months to December 27 – well ahead of most analysts’ expectations.

In a conference call with financial analysts Apple’s chief executive Tim Cook said that demand for phones was “staggering”.

However, sales of the iPad continued to disappoint, falling by 18% in 2014 from a year earlier.

The demand for Apple’s larger iPhone 6 Plus model appeared to help boost profits and increase the iPhone’s gross profit margin – or how much Apple makes per phone – by 2% to 39.9%.

However, Apple did not give a breakdown of sales for the iPhone 6 and other models.

Apple shares rose more than 5% in trading after the US markets had closed.

Apple’s revenue grew to $74.6 billion in 2014 – a 30% increase from a year earlier.

However, on a conference call to discuss earnings, Tim Cook complained of “fierce foreign exchange volatility”, which added Apple to a growing list of US firms who have been hurt by the strong dollar abroad.

Apple said that currency fluctuations shaved 4% from its Q1 2015 revenue.

Sales in greater China hit $16 billion in 2014 – a 70% increase from a year earlier, and almost equaling the $17 billion in sales the company recorded in Europe last year.

A report by research firm Canalys released on Tuesday said that Apple had overtaken competitors to become China’s number one seller of smartphones by units shipped in the fourth quarter of 2014.

Apple also said that its newest product, the Apple Watch, was still on schedule and would begin shipping in April.

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