Democratic groups and figures weren't the only ones targeted in Russia’s suspected campaign to influence last year's U.S. election. Russian cyberspies also targeted computers from state-level Republican groups and stole information from local voter registration records, FBI director James Comey said.

"There were successful penetrations of some groups and campaigns, particularly at the state-level on the Republican side," Comey said during a senate committee hearing on Tuesday.

He and three U.S. intelligence chiefs spoke at the hearing, following their Friday report accused the Kremlin of ordering a covert campaign that helped boost incoming President Donald Trump's election chances.

As part of that campaign, the hackers stole sensitive files from the Democratic National Committee, in addition to an aide to presidential candidate Hillary Clinton, and leaked them online.

On Tuesday, Comey discussed other targets Russian cyberspies allegedly hacked. Among them, were state-level voter registration records that included name and address information.

"What the purpose of those intrusions was is not clear," Comey said. "But there’s no doubt the Russians attacked, intruded, and took data from some of those systems."

Any alteration to a voter registration database might sow chaos on election day, he said. "Someone shows up to vote and your address is different," he said. "That creates delay, controversy, and confusion."

Comey also said that Russian hackers had targeted old email domains belonging to the Republican National Committee. Although the breached domains were no longer in use, the hacker nonetheless "harvested" information from them, he said.

Despite the hacking efforts, no evidence was found showing Russia ever breached vote tallying systems or altered any votes during the election, U.S. intelligence chiefs said.

Comey also said there was no sign that Russia ever hacked Trump’s campaign.

U.S. intelligence agencies have so far declined to release evidence proving the Kremlin’s involvement in the hacks, citing the need to protect its methods. But the intel gathering relied on "multiple high-quality sources," including human ones and technical collection, U.S. Director of National Intelligence James Clapper said during the hearing.

Russia, however, has denied any involvement in the hacks. On Monday, a Kremlin spokesman said the unfounded accusations were driving a "witch hunt."

Trump has also remained skeptical over Russia's suspected role in the hacks. Nevertheless, some U.S. lawmakers have been urging the incoming administration to take greater action and punish the Kremlin.

"This sounds like a pretty effective and successful effort to sow chaos," Senator Marco Rubio, a Florida Republican, said during Tuesday's hearing. "In essence, it sounds like they achieved what they wanted: to get us to fight against each other over whether our elections were legitimate."