Twenty people were injured when a promotional stunt in Seoul for LG's new G2 smartphone went wrong, according to the Korea Times newspaper.
LG has cancelled a series of events promoting the handset as a result of the incident.
People arrived with BB guns and knives on sticks for a race to grab smartphone vouchers hanging from helium balloons.
Some of those hurt in Seoul on Friday were hospitalised, and LG has said it will cover related medical costs.
In a statement, the company said that other planned events had been called off because of safety concerns.
LG released 100 helium balloons, each with a free smartphone voucher, at the so-called G in the Cloud event, which took place in an outdoor park in the Korean capital city.
The phones, which sell for KRW 950,000 in South Korea ($851; £550), would be given to people in possession of the voucher, the company said.
Customers arrived with BB guns to shoot down the balloons and surged forward when they were released.
One person carried a pointed staff to the event.
One regional TV channel has dubbed the scrum "World War G" - a comparison to the film World War Z in which zombies scramble over each other to climb over a wall.
The handset was released in New York last week, after weeks of build-up on social media.
It is expected to be available globally with more than 130 carriers within several weeks.