In the first open U.S. Senate intelligence hearing since federal officials released to the public a declassified account of Russian hacking prior to the 2016 presidential election, Chairman U.S. Sen. Richard Burr said Tuesday that American values are "under assault," but he tried to send a reassuring message that "our democracy is not at risk."

"I know that the public disclosure of these activities surprised many," Burr said. "The notion that another state would attempt to interfere in our elections is troubling."

The Republican senior senator from North Carolina said he doesn't doubt U.S. intelligence agency findings of deliberate Russian interference to discredit Democratic presidential nominee Hillary Clinton and, more broadly, to attempt to undermine confidence in the U.S. government.

Burr promised the Senate Intelligence Committee will conduct an independent, bipartisan review of what the CIA, the FBI and the director of national intelligence call a multifaceted and aggressive "influence campaign," directed by Russia's highest-ranking government officials and President Vladmir Putin.