LIMA, Peru, Aug. 16 — A powerful earthquake shook Peru Wednesday night, killing at least 337 people, Civil Defense authorities said today. More than 800 people are believed to have been injured.

Most of the reported dead were in the region near Ica, south of the capital, which emergency workers said was the hardest hit area. The earthquake, whose magnitude was estimated at 7.9, was centered off Peru’s Pacific shore near Ica.

Many people were killed in the rubble of their homes, and about 200 people were buried under a collapsed church.

Office workers in Lima fled tall buildings that shook in two waves that lasted around 20 seconds each and cut power lines, Reuters reported.

“I was in class on the fifth floor, and suddenly everything started to shake and glass began falling,” said Carolina Montero, 37, a banking administrator and finance student who lives in Callao, a coastal city near Lima. “People got extremely nervous.”

Ica was blacked out, as were smaller towns along the coast south of Lima. Rescue workers reported difficulty getting to Ica because of cracks in the highway and downed power lines.

At least 200 people in Pisco were crushed under the rubble of a church that collapsed during a religious service, The Associated Press reported, citing the mayor of Pisco, Juan Mendoza.

The United States Geological Survey said the earthquake struck about 90 miles southeast of Lima at a depth of about 25 miles. Four strong aftershocks ranging from magnitudes of 5.4 to 5.9 followed.

A tsunami warning was issued for Peru, Chile, Ecuador and Colombia, and a small tsunami was detected, but it posed no major threat and the warning was later lifted, news services reported.

The last time a quake of magnitude 7.0 or larger struck Peru was in September 2005, when a 7.5 magnitude earthquake rocked Peru’s northern jungle, killing four people. In 2001, a 7.9-magnitude quake struck near the southern Andean city of Arequipa, killing 71 people.