The 5.4 magnitude rocked the coast near Pohang in South Korea in the sea of Japan.

The earthquake shook buildings and caused books to fall from shelves sending tremors as far as Seoul – kilometres away from where it struck.

At least four people have been injured, disaster officials confirmed.

The quake occurred at around 2.29pm local time and a series of aftershocks were felt soon after, the Korea Meteorological Administration said.

Mark Zastrow, who lives in Seoul, tweeted: “Woah, earthquake in Pohang and just felt it in Seoul, a few seconds after I got the alert on my phone.”

According to a US Geological Survey (USGS) chart the intensity, tremors would have been felt in North Korea.

An earthquake in the area has raised fears North Korea may have launched another missile test.

In September experts were monitoring Pyonggang after Kim Jong-un triggered an earthquake with one of his tests.

The head of the nuclear test monitoring agency CTBTO has said that its analysts were “looking at unusual seismic activity” in North Korea.

Reports of buildings shaking and tremors being felt 270 km away from Pohang, as well as the island of Jeju.

The region is home to nuclear power plants and industrial facilities, but there has been no word yet of any damage to them.

In Pohang about 100 residents were forced to flee from a residential block. Students in nearby schools were also evacuated from classrooms.

The quake is the second biggest to ever hit South Korea. A 5.8 magnitude quake in September last year was recorded as the most powerful the country has suffered.

Korea Hydro & Nuclear Power (KHNP) told the Korea Herald the six nuclear reactors in Gyeongju, about 45 kilometres south of the epicentre, as well as other reactors on the southeastern coast were all functioning normally.

The KHNP said in a statement: “All reactors, including those in Gyeongju, are operating normally without power shutdown or decreased power output.

“Although there is no breakdown in facilities or radiation leakage, we will conduct an in-depth inspection and release the result later.”

South Korean officials are trying to assess the damage according to local media.

South Korea's Prime Minister Lee Nak-yon ordered the Interior Ministry to do everything to help victims. President Moon Jae-in, who was returning from a Southeast Asian trip, was scheduled to preside over an emergency meeting at Cheong Wa Dae later in the day.

North Korea and South Korea are located in the region known as the Ring of Fire – which extends around the Pacific Ocean and is a hotspot for earthquake activity.

The news comes after the east coast of Japan was rocked by a 5.8 magnitude earthquake on Monday.

The quake hit 18 miles (351 km) east of Sendai, Honshu, at a depth of 5.9 miles (9.5 km) in the Pacific Ocean.

The USGS initially recorded the quake as having a 6.1 magnitude but this was later downgraded.

The Japanese Meteorological Agency said it did not believe the quake’s intensity was strong enough to cause any damage to the land.