Samsung Electronics' Galaxy S3 became the world's best-selling smartphone model last quarter, pushing aside Apple Inc's iPhone, which has dominated the chart for more than two years, research firm Strategy Analytics said on Thursday.

Strategy Analytics estimated Samsung sold 18 million S3 models in the third quarter, compared with iPhone 4S sales of 16.2 million.

Strong sales of the flagship Galaxy S3 - which comes with a large 4.8 inch touchscreen - helped Samsung post a record $7.3 billion operating profit in the July-September quarter.

"Samsung's Galaxy S3 has proven wildly popular with consumers and operators across North America, Europe and Asia," said analyst Neil Mawston, adding the new iPhone 5 would likely reclaim the top spot for Apple in the current quarter.