President Moon Jae-in ordered the strike, by four F-15K fighter-bombers, at a firing range in the country's east to "display a strong capability to punish" North Korea if it were to attack.
The MK-84 multi-purpose bomb is a 2,000lb munition that can penetrate some 11m of earth and 11ft of concrete. South Korea said all eight hit their targets at a testing ground on the country's own soil.
The Yonhap news agency said government officials wanted to show Seoul's ability to overwhelm its belligerent neighbour in the case of all-out hostility.
Pyongyang's test of an intermediate-range ballistic missile that flew over Japan's northern Hokkaido island was condemned by Tokyo as an "unprecedented, serious and grave threat" to the region. "We will do our utmost to protect people's lives," Japanese Prime Minister Shinzo Abe said.
It came amid joint US-South Korean war games.
The launch was the first-ever reported from Sunan, home to Pyongyang's international airport, prompting speculation the North had fired a road-mobile missile from an airport runway.
Runways could provide the ideal space to launch a road-mobile missile like the Hwasong-12, while also demonstrating that the North can launch its missiles from anywhere, according to Moon Seong Mook, a former South Korean military official and current analyst for the Seoul-based Korea Research Institute for National Strategy.
In an unusual move, South Korea's military released footage of its own missile tests it said were conducted last week. The videos showed two types of new missiles with ranges of 800km (497 miles) and 500km (310 miles) being fired from truck-mounted launchers during three tests conducted on 24 August.
South Korea's Agency for Defense Development said the launches represented the last flight test for the longer-range missile before it is operationally deployed.
Such projectiles, which would be the latest additions to South Korea's Hyumoo family of missiles, are considered key components of the so-called "kill chain" pre-emptive strike capability the South is pursuing to counter the North's nuclear and missile threat.
The despot has for months traded barbed remarks with US President Donald Trump, who earlier this summer threatened "fire and fury" if the North continued to threaten the US and its allies.
Mr Kim has warned he could bomb the US Pacific territory of Guam, and Mr Trump declared on Twitter that Washington's "military solutions are now fully in place, locked and loaded, should North Korea act unwisely".
The North has conducted launches at an unusually fast pace this year—13 times, Seoul said—and some analysts believe Pyongyang could have viable long-range nuclear missiles before the end of Mr Trump's first term in early 2021.
South Korea, Japan and the US are desperately trying to bring Pyongyang to the negotiating table to forestall that possibility. Mr Trump has attempted to pressure China, the North's sole major ally, into using its influence to help in the cause.
Additional reporting by agencies
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