SAO PAULO — A Brazilian government institute says the nation has many more homicides than officially reported.

The government-run Economic Research Institute says in a Monday report that its analysis of a national database of death certificates shows there are 8,600 more homicides a year than reported.

That would give Brazil more than 60,000 homicides a year, an increase of nearly 18 percent over official statistics.

The report says the difference arises because many violent deaths in Brazil are erroneously classified on death certificates as having "undetermined causes." Roughly 10 percent of violent deaths in Brazil are classified this way.

The institute examined data from 1996 to 2010. It developed a statistical model based on socio-economic and geographic factors to make a more accurate estimate on how many homicides Brazil has each year.