The powerful earthquake that struck off the coast of Indonesia caused panic throughout the Indian Ocean region, where 300,000 people were killed in the tsunami in December.
In the Indonesian province of Aceh, people sought higher ground
Thousands of people in Indonesia, Malaysia, Thailand, India and Sri Lanka fled to higher ground, but were later told the threat of a tsunami had passed.
Warnings were also issued in Madagascar and the island of Mauritius off the coast of Africa.
Hundreds of people were killed on the small Indonesian island of Nias, off the coast of Sumatra.
In the town of Gunungsitoli, 80% of buildings were damaged.
"From the window I see very high flames," a missionary based outside the town, Father Raymond Laia, was quoted as saying.
"The town is completely destroyed."
In the province of Aceh, the region worst-hit by December's disaster, people fled their homes still in their night clothes.
"People are still traumatised, still scared, they are running for higher ground," Feri, 24, from Banda Aceh, Indonesia, told the Associated Press.
Some walked, clutching their belongings, while others left in minivans or on motorbikes, heading for the hills. People chanted "Allahu akbar", or "God is great."
"I felt the earthquake and I just jumped on my motorbike," said Wayu, who lost his parents and five other family members three months ago.
"I really thought there would be another tsunami. As I drove, I was thinking of those relatives I lost."
But many of those who survived December's disaster refused to leave.
"Where are we going to go?" asked one resident of Ulee Lheu, on the west coast of Sumatra. "You can't outrun the tsunami.
In the Thai resort of Phuket, which was badly hit in December, hundreds of people fled their beds and gathered in the town hall. Some people slept outside or in vehicles.
Others made for higher ground.
"I was told by my boss that the tsunami might happen, so I and other people went up to the hills nearby," Apichart Kongkheun told Thai television.
In India, an alert was issued in the Andaman Islands and along the southern coast.
A Red Cross official in the southern state of Tamil Nadu said people had run inland following the quake reports.
"All the people living near the sea shore are running away after they saw what appeared on television [the warnings]," Mr Illakuvan told AFP.
"They are so scared. They have taken whatever [of their] little belongings in their make-shift shelters and are running far away from the sea."
In Sri Lanka's capital Colombo, Buddhist temples switched on their loudspeakers to broadcast hymns seeking blessings and protection.
"It was like reliving the same horror of three months ago," Fatheena Faleel said.
Caught by surprise
The tremors were felt as far away as Kuala Lumpur, Malaysia, which is some 500km from the quake's epicentre off the Sumatran coast.
"I was getting ready for bed, and suddenly, the room started shaking," said resident Jessie Chong.
"I thought I was hallucinating at first, but then I heard my neighbours screaming and running out."
"It felt stronger than on 26 December," said Arumugam Gopal, a
resident of Penang.
People in Singapore also seem to have been caught by surprise by the tremors.
"I was at my computer when I felt dizzy, and I thought I was swaying in my chair. I thought I had stayed up too late and was perhaps hallucinating," said Lancelot Lee in Singapore.