The Ministry of Information and Communication said in a statement that all three local mobile carriers, including SK Telecom, second-ranked KTF Co Ltd and third-ranking LG Telecom Co Ltd, were unfairly limiting subscribers' access to other firms' wireless Internet services via their handsets.
"We issued SK Telecom, KTF and LG Telecom orders to correct irregularities in providing wireless Internet services and fined SK, which committed serious violations of rules, a total of 1.5 billion," the statement said.
The punishment comes as local operators, faced with stalled growth and cut-throat competition, focus on lucrative wireless Internet services.
The ministry said the firms designed mobile phones with keys that only take users to sites for their own wireless Internet services and used other barriers to make it difficult to access services provided by others.
SK also overcharged its subscribers for using competitors' services, it added.
Wireless Internet services generated 24 percent of SK Telecom's total revenue in the second quarter.