Indonesia has issued a tsunami warning after a powerful earthquake struck of the coast of Sumatra.
The warning is for West Sumatra, North Sumatra and Aceh after a powerful and shallow earthquake of magnitude 7.9 struck off the west coast of the Indonesian island of Sumatra on Wednesday, the National Meteorolgical Agency said.
USGS originally put the magnitude at 8.2, and then 8.1, before lowering it to 7.9.
Indonesia, especially Aceh, was badly hit by the Indian Ocean tsunami in 2004.
The country straddles the so-called "Pacific Ring of Fire", a highly seismically active zone, where different plates on the earth's crust meet and create a large number of earthquakes and volcanoes.
A powerful and shallow earthquake of magnitude 8.1 struck off the west coast of the Indonesian island of Sumatra on Wednesday, the U.S. Geological Survey said.
The epicentre was 502 miles southwest of Padang and it was six miles deep, USGS said.
There were no immediate reports of damage or casualties but the shallower a quake, the more likely it is to cause damage.
Britons in Indonesia have been warned to "maintain vigilance" after terror attacks in the capital Jakarta.
Foreign Secretary Philip Hammond condemned the "utterly senseless acts of terror".
"My thoughts are with the victims and their families," said Mr Hammond.
"We advise British nationals in Jakarta and elsewhere in Indonesia to maintain vigilance and monitor FCO travel advice, local media and to follow the advice of local security authorities."
So-called Islamic State has claimed responsibility for the Jakarta attacks, which were "targeting foreign nationals and security forces".
The announcement was made on an IS-allied news agency.
The police chief in the Indonesian capital has also said the group is "definitely" behind the attack.
An eyewitness to the Jakarta attacks has described panic in the streets following the first explosions.
Australian Andrew Gadd, who works in the Indonesia capital, told ITV News he heard a loud bang while in his office and then someone began shouting "bomb, bomb, bomb".
He said when he looked out of a window he saw another explosion and people running in the street.
"You could see people running away and ducking and hiding behind cars," said Mr Gadd.
ITV News Security Editor Rohit Kachroo tweets:
Indonesian authorities had expected an attack: 150,000 security personnel deployed, arrests made, talk of 'credible threat' over recent wks
Authorities say Jakarta attackers imitated the Paris terrorists. Assumption perhaps. But they can't yet say for sure whether IS responsible
Before Xmas, Australians Attorney-General said IS wanted a 'distant caliphate' in Indonesia.... Great deal of skepticism about comments
Few hundred Indonesians have gone to Syria to join IS/other groups - perhaps 500. Many more Brits are thought to have gone
Figures suggest Indonesian authorities have been relatively successful in combatting draw of extremism - relative to UK for one
Militants who attacked a busy shopping area in downtown Jakarta were copying the Paris attacks, authorities have said.
Indonesia's national police spokesman also said they probably had connections to so-called Islamic State.
General Anton Charliyan said: "They imitated the terror actions in Paris...they are likely from the (Islamic State) group."
Indonesian police have arrested four suspected militants following the gun and bomb attacks in the centre of the capital Jakarta.
Five assailants were confirmed dead, along with two other people.
Police declared the area secure shortly before 8am GMT after sweeping through the area.
Jakarta police spokesman Col. Muhammad Iqbal said: "We believe there are no more attackers around Sarinah. We have taken control."
Militants have launched a series of co-ordinated bomb and gun attacks in the Indonesian capital Jakarta. Here's what we know so far.Read the full story ›
Surveillance footage has emerged showing an explosion outside a Starbucks in central Jakarta.
The area around the explosion appeared quiet, with no pedestrians in sight.