A tsunami reaching as high as 85 centimeters has been observed off South Korea's east coast in the aftermath of a powerful magnitude-7.6 earthquake in Japan's Noto Peninsula, the weather agency said Tuesday.

The quake struck the Noto Peninsula and surrounding areas in Japan's Ishikawa Prefecture on New Year's Day, reportedly killing several people and prompting thousands to evacuate. A major tsunami warning was issued.

About four hours after the quake, a tsunami wave, measured at 85 cm at its highest point, was observed off the port of Mukho in the eastern coastal city of Donghae, 182 kilometers east of Seoul, at 8:35 p.m. on Monday, according to the Korea Meteorological Administration.

Between 8 p.m. and 9 p.m. on Monday, tsunamis of a smaller scale were also observed along the east coast, with the nearby cities of Sokcho and Samcheok experiencing waves as high as 45 cm and 33 cm, respectively. The county of Uljin along the lower part of the east coast saw the tsunami waves rise as high as 66 cm.

Following the Monday quake, the first tsunami was observed off South Korea's eastern coast in less than two hours, in the coastal city of Gangneung, where the waves were measured as high as 39 cm.

The KMA said tsunamis with waves lower than 10 cm had been surging toward the east coast as of 8 a.m. Tuesday, adding that tsunamis were gradually ebbing but people on shore areas still have to take caution.

"If no stronger earthquake occurs, it is unlikely that tsunamis higher than those observed so far will come in," a KMA official said.

It marks the first time South Korea has experienced a tsunami on its coasts since July of 1993, when a magnitude-7.8 earthquake off Japan's Hokkaido sent tsunamis toward the South Korean east coast measuring 2.76 meters at the highest point. (Yonhap)