Permits to buy handguns in New Jersey—which has some of the strictest firearms laws in the U.S.—increased by 67% through June compared with the same period in 2012, according to data provided by the state police.

New Jersey issued 59,120 permits required to purchase handguns in the first six months of 2013, the data show. Through June 2012, 35,425 permits were issued, and 64,107 were obtained for the entire year.

Experts, gun-rights groups, and new gun owners described the increase as largely inspired by fears that state and federal firearms policies would tighten. The surge also follows the Dec. 14 school shooting in Newtown, Conn., where 20 children and six adults died and which sparked a national debate about U.S. gun laws.

Business in 2013 has been "absolutely ridiculous," said Gerry Morey, a firearms dealer in Bayville, N.J. "The biggest part of my clientele increase has been for personal protection handguns and personal protection shotguns."

The sharp rise in permits shows that "even in the state that has some of the strictest gun laws in America, it's really easy to get a gun," said Todd Clear, dean of Rutgers University School of Criminal Justice. New Jersey was given an A- from the Law Center to Prevent Gun Violence for its firearms policies.