A strong earthquake has hit the Nicobar Islands in India but there are no reports of major damage or casualties.
The islands are still reeling from the tsunami in December
With memories of December's tsunami still fresh, Thai authorities briefly issued a tidal wave alert, but within two hours had withdrawn the warning.
The magnitude-7 quake occurred at 1542 GMT about 135km (85 miles) west of Misha, Nicobar Islands, and 440km (275 miles) from Banda Aceh, Indonesia.
It was felt as far away as Madras (Chennai), India, and Phuket, Thailand.
It is the second time the Thai authorities have issued such a warning since the 26 December tsunami.
Near the Thai beaches of Bangtao, Surin and Karon, eyewitnesses said people had taken to higher ground in the darkness because of the warning.
"The quake lasted about 15 seconds," said an official at the police control centre in Port Blair, capital of the Andamans.
But the impact of the quake was felt more intensely in the Nicobar islands.
Residents there say the earth shook violently and there was some damage to buildings, even the newly constructed tin shelters for December's tsunami victims.
"There was panic in the islands of Nicobar," said DN Singh, an official at Kamorta, in the Nicobars. "We felt another deluge is coming, but thankfully, this has passed without much trouble."
Officials at the Andaman and Nicobar Centre for Ocean Development, Ancod, told the BBC there was no tsunami threat for the archipelago this time.
"We have watched the aftermath of the quake and unless there's a fresh tremor of similar intensity, we don't anticipate a tsunami," said an Ancod official.
In Sri Lanka, where more than 30,000 people died in December's tsunami, the meteorological department said there was no need to issue a tsunami alert.
The Andaman and Nicobar islands are still reeling from December's quake and tsunami which killed nearly 4,000 people, according to official records.
Unofficial sources say twice as many people perished in the remote islands , particularly in the Nicobars.
The tsunami killed at least 200,000 people in 13 countries. Most of the victims were in Indonesia's Aceh province.