A 6.1 magnitude earthquake shook northern Peru Monday, causing alarm but no damage or casualties, authorities said.

The quake struck at 4:49 am (0949 GMT) in the Pacific Ocean 93 kilometers (57 miles) west of the coastal city of Paita at a depth of 17 kilometers (10 miles), the Geophysical Institute of Peru said.

The US Geological Survey said the quake had an intensity of 6.1 on the Moment magnitude scale. Peruvian seismologists measured it at 5.8 on the Richter scale.

Peru's civil defense agency said the quake caused no casualties or damage.

Medium intensity quakes are common in Peru, which is located on the Pacific basin's so-called "ring of fire," with 130 reported this year.