(Adds details from USGS, eyewitness)
MANAGUA, April 10 (Reuters) - A strong earthquake shook the Nicaraguan capital of Managua on Thursday, knocking out telephone lines and power in some areas, a Reuters witness said, and the government was checking for any damage.
The quake had a magnitude of 6.1, the U.S. Geological Survey said, and was very shallow at a depth of 6.2 miles (10 km). It was previously reported as having various magnitudes ranging up to 6.4.
The earthquake struck at 2327 GMT, 19 miles (31 km) northeast of the town of Nagarote or 31 miles (50 km) north-northwest of the capital Managua, USGS added.
The Reuters witness said there was a small aftershock.
A magnitude 6.1 quake is capable of causing severe damage. (Reporting by Ivan Castro; Writing by Christine Murray; Editing by Simon Gardner and Eric Walsh)