They provided the service to selected users, including famous artists, sportsmen and television presenters.
Among South Korea's top three telecom operators, SK Telecom and KT Corp do not use Huawei equipment for 5G services.
World estimates predict that 5G service will generate incomes by 2035 $3.5 billion United States dollars and 22 million jobs worldwide.
But according to Yonhap, the South Korean launches came two hours earlier. - The world's biggest smartphone and memory chip maker Samsung Electronics warned of a 60 percent-plus plunge in first-quarter operating profits on April 5, in the face of a weakening chip market.
For general customers, the services will be available from Friday - the original launch date - when Samsung Electronics rolls out the Galaxy S10 5G, the world's first available smartphone with the technology built in.More news: Why is WikiLeaks founder Julian Assange in Ecuadorian embassy?
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The implications of the new technology have pitted Washington against Beijing - whose firms dominate 5G technology - in an increasingly bitter standoff.
Korea could have lost the race to become the first country to commercialize 5G telecommunications in the world.
The telecoms have been in a fierce fight with their U.S. rivals.
Park Jung-ho, CEO of SK Telecom, talks up the operator's 5G offering on Wednesday at what SKT called the "beginning of the Age of Hyper-Innovation with 5G" at the company's 5G Launching Showcase. The US carrier lacks actual 5G phones and can only offer the high-speed services to customers with a Motorola Z3 handset who pay $50 extra for a Snap-on module.
South Korean carriers have spent billions on campaigns marketing 5G and, on Wednesday, SK Telecom showed off K-pop stars and an Olympic gold medallist as its first 5G customers.
Mobile carriers are competitively developing and introducing photorealistic live streaming services and virtual reality experiences to prove that 5G network is a change that is worth the cost of purchasing a new phone and plan. Users will get more data faster, with less delay.