South Korean telecom operator KT Corp said on Sunday it planned to begin selling Apple's iPhone 4 this week amid growing competition to expand in the potentially lucrative smartphone market. KT, the country's sole distributor for the gadget, plans to start sending out the gadgets on September 10 to around 270,000 customers who placed pre-orders, a company spokesman said. 'Our branches will also start selling the phones after the pre-ordered items are shipped off,' he said. KT, South Korea's second-largest wireless operator, has sold about 890,000 iPhones since the market debut of earlier models last November. And tens of thousands of people jammed the company's website on August 18 as it started accepting online orders for the latest model of the popular smartphone. Local competitors such as Samsung Electronics and LG Electronics have been striving to compete by introducing new smartphones, including the Galaxy S and Optimus series. Samsung said Wednesday it has sold more than one million units of Galaxy S since the firm's signature smartphone model hit the market in June. South Korea's mobile phone market is one of the world's most vigorous, with 45 million users in a population of 49 million. Smartphones, however, have a relatively small share, suggesting huge growth potential. Samsung Electronics estimated about five million smartphones will be sold in the country by the end of 2010, up from fewer than one million in 2009. 