An AR-15 rifle is displayed at the Stag Arms company in New Britain, Conn., in 2013. (Charles Krupa/AP)

A poll finds that almost two-thirds of American adults under 30 who plan to vote in the midterm elections believe gun-control laws should be stricter, a reflection of growing support for such actions among younger Americans.

The poll by Harvard University’s Institute of Politics, conducted in the wake of the school shooting in Parkland, Fla., finds that 64 percent of 18- to 29-year-olds favor stricter gun-control laws, regardless of whether they plan to vote in November.

That is a 15-percentage-point jump since 2013, months after the elementary school shooting in Newtown, Conn., when polling by the institute found that 49 percent of that group supported stricter laws.

In the new poll, 10 percent said gun laws should be less strict, while 22 percent said they should be kept the same.

The poll also found support for a ban on assault weapons among voting-age Americans under 30 has increased significantly compared with 2013, when 41 percent supported such a ban. Now that figure is 58 percent.

“For several years, the opinions of young Democrats, Republicans and independents have been steadily shifting toward greater support for gun-control measures,” said John Della Volpe, the institute’s polling director. “The difference today is that the Parkland students have created an environment where the lack of progress on reducing gun violence is now symbolic of all the ills plaguing Washington, D.C.”

The institute’s latest poll was conducted in March and with a sample of more than 2,600 people ages 18 to 29 and a margin of error of plus or minus 2.5 percentage points.

Other results have been previously released, including a finding that 37 percent said they will “definitely be voting” in the midterm elections, compared with 23 percent who said the same thing in a 2014 poll.