An earthquake jolted the German town of Koblenz early Friday, but caused no casualties or damage, police said.

The quake, which measured 4 on the Richter scale, roused people from their beds at 5 a.m. It was followed half-an-hour later by a less powerful aftershock.

Hundreds of anxious residents telephoned the emergency services asking for advice, a police spokesman said.

Officials said about 25 to 50 earthquakes occur in the region every year, but most are less than 3 on the Richter scale.

A quake with an intensity of 4 occurs about once every 10 years, said Harald Ehses, director of the regional office of mines and geology.