Reports of sexual assaults in the military increased by an unprecedented 46 percent in the past fiscal year, the Pentagon said Thursday.

It wasn’t possible to know whether the spike represented an increase in assaults, an increase in the number of people reporting them, or both. Defense Department officials portrayed the sharp rise as a sign that people are more confident about coming forward now that improvements are being made to the military’s system for handling assaults.

The military received 3,553 complaints of sexual assault from October 2012 through June, compared with 2,434 reports during the same period the previous year, according to statistics presented Thursday at the start of a two-day public meeting of an independent panel looking into the issue

The report to the Response Systems Panel said an increase in complaints was registered across all service branches — Army, Navy, Air Force and Marines.

And it noted that more reports of sexual assault were made in the first three quarters of fiscal 2013 than the 3,374 reported during the entire 2012 budget year.

“A change in reports of sexual assault may reflect a change in victim confidence in Department of Defense response systems,” said a 14-page slide presentation prepared for the panel.

The department in recent years has started programs aimed at boosting the confidence of victims, including holding awareness training across the forces and adding legal help and more social services for those reporting assaults.

Despite official data reported annually on sexual assaults, the Pentagon acknowledges that the actual number of attacks could be several times higher and that many incidents go uncounted because of reluctance in the military, as in the civilian sector, to report such crimes.

The new data and Thursday’s public meeting come just weeks before the Senate is expected to take up a proposal to change how the military justice system deals with sexual assaults.

The proposed legislation would remove commanders from the process of deciding whether serious crimes, including sexual misconduct cases, go to trial, and it would give that authority to trial lawyers who have prosecutorial experience and hold the rank of colonel or higher.

The chief advocate of the change, Sen. Kirsten Gillibrand (D-N.Y.) is expected to push to attach her measure as an amendment to the annual defense policy bill that the Senate is expected to consider the week of Nov. 18.

Forty-six senators support the proposal, including 38 Democrats and eight Republicans. But her idea is opposed by the Pentagon, Senate Armed Services Committee Chairman Carl Levin (D-Mich.) and Sen. Claire McCaskill (D-Mo.).

Levin agrees with the Joint Chiefs of Staff that commanders should remain involved in deciding whether to prosecute sexual assault cases. Military leaders have argued that removing the decision from their purview would undercut officers’ ability to maintain order and discipline in their units.

— Associated Press