Washington (CNN) A group of US senators, including the vice chair of the Senate Intelligence committee, received a classified briefing Wednesday about a series of reported encounters by the US Navy with unidentified aircraft, according to a congressional aide.

"If pilots at Oceana or elsewhere are reporting flight hazards that interfere with training or put them at risk, then Senator Warner wants answers. It doesn't matter if it's weather balloons, little green men, or something else entirely — we can't ask our pilots to put their lives at risk unnecessarily," Rachel Cohen, the spokeswoman for Democratic Virginia Sen. Mark Warner, told CNN.

Joseph Gradisher, spokesman for the Deputy Chief of Naval Operations for Information Warfare, also confirmed the briefing took place in a statement to CNN on Thursday.

"Navy officials did indeed meet with interested congressional members and staffers on Wednesday to provide a classified brief on efforts to understand and identify these threats to the safety and security of our aviators," he said.

"Follow-up discussions with other interested staffers are scheduled for later today (Thursday, 20 June). Navy officials will continue to keep interested congressional members and staff informed. Given the classified nature of these discussions, we will not comment on the specific information provided in these Hill briefings," Gradisher added.