Tokyo, Apr 18 (IANS): At least nine people were injured after an earthquake with a magnitude of 6.6 struck a wide area of western Japan, local authorities said on Thursday.

The quake struck at around 11:14 p.m. local time, registering lower 6 on the Japanese seismic intensity scale of 7 in Ehime and Kochi prefectures, both on Shikoku Island, with the epicentre in the Bungo Channel, a strait separating the islands of Kyushu and Shikoku, the Japan Meteorological Agency said as quoted by Xinhua news agency report.

According to prefectural governments and local fire departments, six people in Ehime Prefecture and one person in Kochi Prefecture sustained minor injuries, while two were hurt in Oita Prefecture in the Kyushu region, southwestern Japan.

A valve defect reduced the power output of the No.3 reactor at the Ikata nuclear complex in Ehime Prefecture by two per cent, though there was no major problem with overall operations, Shikoku Electric Power said.

Meanwhile, Japanese researchers warned that earthquakes could continue for another week or so following the powerful temblor, and people in the region should stay alert, Japanese daily Mainichi Shimbun reported.

According to Takuya Nishimura, a professor at Kyoto University's Disaster Prevention Research Institute specialising in geodesy, which involves measuring Earth's geometry, said the area near the Bungo Channel has experienced quakes in the past that caused significant damage.

"We need to prepare for earthquakes, keeping in mind that they will continue for the next week or so," the researcher warned.