An earthquake with a magnitude of 6.6 hit a wide area in western Japan on Wednesday night but no tsunami warning was issued and there were no immediate reports of major damages or fatal casualties, the Japanese government said.

The 11:14 p.m. quake registered lower 6 on the Japanese seismic intensity scale of 7 in Ainan, Ehime Prefecture, and Sukumo, Kochi Prefecture, both on Shikoku Island, with its focus in a strait separating the island from the southwestern main island of Kyushu at a depth of 39 kilometers, according to the weather agency.

It was the first quake to reach the intensity level in the island of Shikoku, located on Japan's Pacific coast, since the current scale was set in October 1996, the Japan Meteorological Agency said.

Fallen roof tiles lie scattered on a street in Uwajima, Ehime Prefecture, on the morning of April 18, 2024, following a strong earthquake the previous night. (Kyodo)

The quake's focus in the Bungo Channel fell within part of an area where a governmental panel said a devastating temblor with a magnitude of at least 8.0 could occur within 30 years. The area is near the undersea Nankai Trough, which stretches from off Shizuoka Prefecture in central Japan to off Miyazaki Prefecture in the country's southwest.

But an official of the agency told a press conference that Wednesday's quake was not a direct indication that there is a greater likelihood of such a strong earthquake occurring near the trough.

The quake appeared to have occurred in the Philippine Sea Plate and its seismic mechanism was different from that of a potential Nankai Trough quake, the agency said.

As the government continued to gather information on quake damage, there were reports of buildings with broken windows, ruptured water pipes and dangling power cables in the area, according to local authorities.

Several people were taken to hospital, Chief Cabinet Secretary Yoshimasa Hayashi said at a separate press conference, and he called on the public to continue to brace for aftershocks with a level of lower 6 on the scale.

Hiroki Tachibana, a 60-year-old head of a local fishery cooperative in Ainan, was awakened by shaking that lasted for more than 10 seconds. He also heard creaking sounds from his two-story wooden home.

Chief Cabinet Secretary Yoshimasa Hayashi briefs reporters on the latest information about a magnitude-6.4 earthquake that hit a wide area of western Japan at the prime minister's office in Tokyo on April 18, 2024. (Kyodo)

"I'm worried about whether fishery cooperative facilities have been affected," he said.

The quake caused no major damage to the Ikata nuclear power plant in Ehime Prefecture, the operator Shikoku Electric Power Co. said.

Kyushu Electric Power Co. also said no abnormalities had been detected at the Sendai nuclear power plant in Kagoshima Prefecture on Kyushu Island.

Near the Nankai Trough, a magnitude-8 class quake has occurred at certain intervals for centuries. The government's Earthquake Research Committee forecasts a 70 to 80 percent likelihood that a quake with a magnitude of 8.0 to 9.0 will occur there within the next 30 years.

Related coverage:

Kumamoto marks 8th anniversary of deadly quakes

M5.1 quake hits southwestern Japan, no tsunami warning issued