The U.S. Geological Survey said the temblor, which followed a deadly 7.4-magnitude quake that hit the same region Wednesday, was recorded at 4:15 p.m. local time at a depth of 16.8 miles. There were no immediate reports of casualties, the Guatemalan newspaper Prensa Libre reported.
The epicenter was 14 miles west-southwest of Champerico, Guatemala, 24 miles south-southeast of Suchiate, Mexico, 31 miles south of Ciudad Tecun Uman, Guatemala, and 36 miles southwest of Flores Costa Cuca, Guatemala, the USGS said.
Prensa Libre said the shaker was felt just as President Otto Perez was providing reporters with an update on last week's quake that killed at least 52 people.
The newspaper said people in San Marcos ran into the streets in apprehension.