SEOUL, Jan 1 (Reuters) - A tsunami measuring under one metre (3.3 ft) reached South Korea's east coast in the wake of a massive earthquake that hit Japan on Monday, South Korea's meteorological agency said, which added there may be more and larger waves in the next hours.

The first tsunami to reach South Korea's coast was 67 cm (2.2 ft) but it may increase in size after the initial waves and may continue for more than 24 hours, the meteorological agency said

Separately, North Korea issued tsunami warnings for its coast of possible waves of more than 2 metres, South Korea's Yonhap news agency reported, citing the North's state radio.

South Korea's Gangwon province warned residents to take precautions and evacuate to higher ground, according to the Ministry of Interior and Safety.

The east coast province told residents in emergency messages to stay away from the coast and evacuate to higher ground. The city of Samcheok advised residents to move to areas higher than a three-storey building, the ministry said.