Chinese smartphone maker OnePlus has notched up an impressive achievement for a company its size: It sold more than one million of its latest smartphone -- the OnePlus 6 -- in just over three weeks.

In comparison, it took the company three months to achieve the same result for its two previous smartphones combined, the company’s founder and CEO Pete Lau told Business Insider.

70 percent of OnePlus’ sales are from outside mainland China. (Picture: SCMP)

Pitched as a price-friendly alternative to premium handsets like the iPhone X and Galaxy S9, the OnePlus 6 has been receiving rave reviews since its launch last month.

“The best flagship killer OnePlus has put out yet,” wrote one reviewer. “The progeny of smartphone royalty has arrived,” noted another.

You get the idea: OnePlus delivers premium, flagship-level phones at reasonable prices. (The OnePlus 6 starts at $530).

That is part of the reason why the company -- founded just over four years ago -- has developed a cult following, particularly among tech lovers (and apparently also employees of Amazon, Facebook and Google).

Another is its software, which is known for its minimal aesthetic and customization -- one reason it may have won over Android fans in the West in ways competitor Huawei hasn’t.

Unlike its sister brands Oppo and Vivo -- whose sales are primarily in mainland China and other developing markets -- OnePlus has found success in the West.

In fact, 70 percent of its sales are from outside the Chinese mainland, with the US and Europe among the biggest markets. Its success in the US is even more surprising when you consider its phones aren’t available through Verizon or Sprint -- two of the country’s biggest carriers.

But it hasn’t always been smooth sailing.

The company was forced to temporarily suspend sales in India because of legal troubles. And it has also been criticised for privacy concerns, including collecting users’ personally identifiable information without permission and for leaving a “backdoor” in some of its phones.