A senior Democratic lawmaker said Sunday he had "no doubt" that Russia was behind recent hacking attempts targeting state election systems, and urged the Obama administration to publicly blame Moscow for trying to undermine confidence in the Nov. 8 presidential contest.

The remarks from Rep. Adam Schiff, the top Democrat on the intelligence committee in the U.S. House of Representatives, come amid heightened concerns among U.S. and state officials about the security of voting machines and databases, and unsubstantiated allegations from Republican candidate Donald Trump that the election could be "rigged."

"I have no doubt (this is Russia). And I don't think the administration has any doubt," Schiff said during an appearance on ABC's "This Week."