Sales of the new model, an upgraded version of the firm's flagship smartphone, had doubled in two months after hitting the five-million mark in July, the company said.
The new device was released locally on April 29 and in some European countries in May. It also went on sale in China in July before hitting the US market in September.
"In just five months the Galaxy S II has seen tremendous growth, reflecting strong support from carrier partners," JK Shin, the head of the firm's mobile device unit, said in a statement.
Shin said earlier this year that Samsung planned to sell globally more than 10 million of the phones, powered by Google's Android operating system and spearheading the firm's smartphone push this year.
Sales at home amounted to 3.6 million followed by 3.4 million in Europe and 2.3 million in rest of Asia, the company said.
The firm, one of the world's major mobile phone sellers competing against companies like Apple, has sold more than 14 million of its Galaxy S smartphone which was released in June 2010.
Samsung and Apple are at loggerheads in a series of patent lawsuits over the technology and design of their smartphones and tablet computers.
Despite their legal battles, Apple is one of the biggest customers for Samsung's chips and display screens.
