Traumatised Algerians have fled the capital Algiers and other built-up areas after a fourth tremor in just over a week hit the country.
The earthquake measuring 5.8 on the Richter scale hit the Mediterranean coast before dawn.
An earthquake in the same region killed more than 2,000 people last week.
Today's quake, which was followed by two smaller tremors during the day, left some people injured and several buildings reduced to rubble, but there were no deaths.
"People are fleeing town. Algiers is empty, everyone's joining their families elsewhere," Kenza Djouhri, owner of an estate agency in Algiers, told journalists.
"My close friends are coming with me to my family's house outside Algiers, which is safe. If we're going to die, we do it together."
Authorities said people should remain calm but not sleep in damaged buildings.
"I urge people to stay calm. It's an aftershock. More will come," said Mohamed Hamadache, a researcher at Algeria's Geophysical, Astronomical and Astrophysics Research Centre.
The official toll from the May 21 quake is 2,251 dead and 10,243 injured, but hundreds are still unaccounted for.
Tens of thousands are now sleeping outdoors in Algiers and the quake zone to its east.
Authorities have made available more than 17,000 tents to accommodate 150,000 people for several months.
The epicentre of Thursday's quake, like the previous ones, was near the town of Zemmouri, some 30 miles east of Algiers, a city of three to four million.