South Korea's largest mobile operator SK Telecom said Tuesday it would invest a record 2.3 trillion won ($2.1 billion) this year to expand its network and meet the growing data needs of smartphone users.

The investment, an increase on the two trillion won originally planned, will be used to build more cellphone towers and upgrade existing , it said in a statement.

"Functions of smartphones are improving so fast and we have to help our data traffic capacity keep up with the phones," a spokesman told AFP.

More of the company's 5.3 million smartphone users were watching movies and large video clips that require far faster data delivery, he said.

Official data showed gadget-mad had about 51 million mobile phone subscribers at the end of February, more than the population of 48.8 million.

Of the total, more than 10 million were smartphone users compared to about 800,000 in December 2009.

Telecommunication authorities say the country will have more than 20 million smartphone users by the end of this year.

(c) 2011 AFP