Japan is located at the junction of four tectonic plates and hence experiences relatively violent earthquakes every year. [Representational Image]Reuters

A second, stronger earthquake measuring 7.3 magnitude struck Japan's Kumamoto Prefecture early Saturday, killing more people after an earthquake on Thursday toppled buildings in the region and forced thousands to evacuate. A tsunami warning was issued on Saturday but was soon lifted, as per reports. 

At least 19 people were confirmed killed in the second earthquake in just over two days, after nine people had been killed in the 6.5 magnitude temblor on Thursday, Kyodo news agency reported. The 7.3 temblor struck the Kyushu region at about 1.30 a.m. local time on Saturday, triggering landslides and more damage. 

According to the U.S. Geological Survey, Saturday's earthquake released 22 times more energy than the one that struck two days ago.  Japanese media had described the previous earthquake as the "strongest since 2011."

About 40,000 people were evacuated from their homes in the Kumamoto Prefecture since Thursday night.

Japan is often hit by earthquakes, which has also raised concerns over the country's nuclear programme, especially since the Fukushima nuclear disaster. There were no reports of irregularities in the nuclear power plants in the region on Saturday. 

Japanese Prime Minister Shinzo Abe was scheduled to visit Kyushu on Saturday to inspect damage and rescue efforts following Thursday's quake, but his trip has been cancelled, AFP reported citing local media. 

Aftershocks continued to jolt the region on Saturday.