WASHINGTON - Gun homicides have dropped steeply in the United States since their 1993 peak, a pair of reports released Tuesday showed, adding fuel to Congress' battle over whether to tighten firearm restrictions.

A study released Tuesday by the government's Bureau of Justice Statistics found that gun-related homicides dropped from 18,253 in 1993 to 11,101 in 2011 - a 39 percent reduction.

A report by the private Pew Research Center found a similar decline by looking at the rate of gun homicides, which compares the number of killings to the size of the country's population. It found that the number of gun homicides per 100,000 people fell from 7 in 1993 to 3.6 in 2010, a drop of 49 percent.

Perhaps because of the intense publicity generated by mass shootings such as the December massacre of 20 schoolchildren and six educators in Newtown, Conn., the public seems to have barely noticed the reductions, the Pew study shows.

The nonpartisan group said a poll it conducted in March showed that 56 percent of people believe the number of gun crimes is higher than it was two decades ago. Only 12 percent said they think the number of gun crimes is lower.

The data were released three weeks after the Senate rejected an effort by gun-control supporters to broaden the requirement for federal background checks for more firearms purchases.

Sen. John Thune of South Dakota, a member of the Senate Republican leadership, said the figures show that gun-control groups have emphasized the wrong approach to controlling firearm violence. He said lawmakers should aim at preventing mass killings by improving mental-health programs and increasing the records that state governments send the federal background-check system.

Gun-control backers said the deaths remain too high.

Though researchers differ over all the reasons gun violence has declined, many attribute it to the aging of the baby boomers. The crime rate was higher in the 1960s and 1970s, when many in that large generation were teenagers, an age when higher proportions of people commit crimes.