A powerful 7.2 magnitude quake shook Ecuador on Wednesday, one month after a much larger quake killed some 700 people, the country's Geophysical Institute said in a preliminary report.

The epicenter of the quake, which struck at 11:47 am (1647 GMT), was located in the northwestern coastal province of Esmeraldas near the border with Colombia, the Institute said.

The US Geological Survey, which monitors earthquakes worldwide, reported that the quake measured 6.8 on the moment magnitude scale and followed a 6.7 earthquake that struck in approximately the same region at 2:57 am local time (0757 GMT).