SAN SALVADOR, El Salvador -- The small nation of El Salvador has recorded another milestone in criminal violence: At least 51 people were killed in a single day this week, the National Civil Police force said Friday.

Thursday's toll surpassed the mark of 45 killed on Aug. 22 as gang violence continues to plague the Central American country of 6 million people.

Authorities have said the surge in violence is a result of a government crackdown that has led to gunfights between police and criminals, as well as gang battles over territory.

Police on Friday also reported finding the body of a slain police officer -- the 45th officer this year to die at the hands of gangs. Sixteen soldiers and six prison guards also have been killed.

The government says 3,942 people were slain in 2014, an increase of 1,429 over 2013.