The death toll from an earthquake that struck Kumamoto Prefecture on the island of Kyushu in Japan has risen to 28, NHK reports.

Japan's chief cabinet secretary Minoru Kihara confirmed at a press conference that as of 6:30 a.m. local time on Thursday, 28 people had died in a series of earthquakes in the Kyushu region.

Earlier, 18 people were reported dead.

On Tuesday, seismologists recorded a 7.1-magnitude earthquake in Kumamoto Prefecture, with the strongest tremors felt in the cities of Uki and Kikawa.