A powerful earthquake with a magnitude of 7.4 - the strongest earthquake in 25 years to hit the island- followed by a smaller quake with a magnitude of 6.5 struck off Taiwan's eastern coast Wednesday, according to the US Geological Survey, prompting tsunami warnings in southern Japan.

The first quake, with a magnitude of 7.4, struck at 7:58pm ET (7:58am local time) and had an epicenter located about 18 kilometers (11 miles) south of the city of Hualien and shook buildings in the capital Taipei.

It's the biggest seismic event by magnitude since 1999, when the so-called 921 quake hit the island and killed more than 2,000 people, Taiwan weather authorities said during a press conference. There have been several aftershocks clustered on the island's east coast.

The second quake, with a magnitude of 6.5, hit 13 minutes later at 8:11pm ET, and was lcoated at almost the exact same spot as the first one: its epicenter was about 11 kilometers northeast of Hualien City.

Hualien announced plans to shut down offices and schools Wednesday in the wake of the event. The island's power provider, meanwhile, said nuclear power plant operations remain normal and power distribution in Taiwan had stabilized.

People on the Chinese social platform Weibo said they felt the quake all across China, including in Shanghai and Guangdong.

Tsunami waves reaching 1-to-3 meters were possible along some coasts of China and Taiwan, the Pacific Tsunami Warning Center said. A tsunami warning was also issued for southwestern Japan's Okinawa prefecture after the region was rocked by the quake.