from India to Kenya, reawakening painful memories of the catastrophic 2004 tsunami that claimed nearly a quarter of a million lives.
The 8.6-magnitude undersea quake and strong aftershocks hit off Indonesia's Sumatra island just a few hundred kilometres from the epicentre of that deadly event, with witnesses saying they felt the ground shake for well over a minute.
In Indonesia's Banda Aceh, which was devastated by the 2004 Boxing Day tsunami, people raced from tall buildings and headed inland as warnings of another destructive tsunami were issued across the region.
The alerts were cancelled several hours later after the waves proved to be limited and at their highest less than a metre.
But in the hours before the all-clear, there were chaotic scenes as people grabbed their families and raced through crowded streets, with motorbikes and cars jostling for space.
"It lasted a very long time," said Australian Steven Sewell in Padang, West Sumatra where he runs a surfing charter business, adding that the quake sparked fear in the streets.
"We headed to higher ground above the river for two hours then the second one (aftershock) hit.
"The second one was almost as long as the first one. Just prolonged shaking from side to side... Pretty scary when your pregnant wife's in the car."
In Sri Lanka which was also hard-hit by the 2004 disaster, thousands fled coastal homes after a tsunami warning was issued across the island and residents were urged to move inland to avoid being hit by any large waves.
"There is a near panic situation," a resident in Trincomalee contacted by telephone said, adding that the port city was packed with last-minute shoppers trying to stock up before the traditional New Year on Friday.
Malaysian state news agency Bernama said the quake was felt across the country including in the capital Kuala Lumpur, and the northern state of Perlis where panicky residents rushed from apartment blocks.
Buildings swayed as far away as the Thai capital Bangkok. Thailand's National Disaster Warning Centre advised people in the area to move to higher places and stay as far away as possible from the sea.
Australian Bonnie Muddle, vacationing on the Thai resort island of Phuket, said people were being evacuated from popular tourist areas including Krabi and Phang Nga Bay amid rumours that towering waves up to six metres high were barrelling towards them.
"Everyone is getting a little concerned over here," she told AFP.
The December 26, 2004 disaster was triggered by a massive 9.1-magnitude earthquake off Sumatra which caused a tsunami that wrought devastation across the Indian Ocean, killing an estimated 220,000 people.
Last year, a 9.0-magnitude earthquake caused a tsunami and nuclear disaster in Japan, killing some 19,000 people.