By Julia Harte and Dustin Volz

WASHINGTON (Reuters) - Federal and state authorities are beefing up cyber defenses against potential electronic attacks on voting systems ahead of U.S. elections on Nov. 8, but few are taking new steps to guard against possible civil unrest or violence.

The threat of computer hacking and the potential for violent clashes is darkening an already rancorous presidential race between Democrat Hillary Clinton and Republican Donald Trump, amid fears that Russia or other actors could spread political misinformation online or perhaps tamper with voting.

To counter the cyber threat, all but two U.S. states have accepted help from the U.S. Department of Homeland Security (DHS) to probe and scan voter registration and election systems for vulnerabilities, a department official told Reuters.

Ohio has asked a cyber protection unit of the National Guard, a reserve force within the U.S. military, for assistance to protect the state's systems.

On Thursday, Arizona Secretary of State Michele Reagan and her cyber security team met with officials from the FBI and the DHS, in addition to state-level agencies, to discuss cyber threats, said Matt Roberts, a spokesman for Reagan.

The National Governors Association on Friday said election officials were well prepared for possible cyber threats and had been confronting them for over a decade.

“We remain confident that any technical problems on Election Night will not undermine the overall integrity of the process,” the association said in a statement.

Unidentified intelligence officials told NBC News on Thursday there is no specific warning about an Election Day attack, but they remain concerned hackers from Russia or elsewhere may try to disrupt the process, likely by spreading misinformation through social media sites.

ARMED GROUPS

The potential for violence around the election has loomed in the background of the campaign for months. Armed groups around the country have pledged in unprecedented numbers to monitor voting sites for signs of election fraud.

Federal officials have warned authorities in New York, Texas and Virginia about an unspecific threat of attacks by the al Qaeda militant group around Election Day, putting local law enforcement on alert before Tuesday's vote.

A U.S. government source in Washington said some federal agencies sent bulletins to local and state officials flagging the information but that the threat was relatively low level.

"We are continuing with the high level of patrols at all of our facilities that we have had in place for some time now,” said spokesman Steve Coleman of the Port Authority, which operates airports, tunnels and bridges around the area.

Voter intimidation reported at polling sites so far prompted Democrats to accuse Trump of a "campaign of vigilante voter intimidation" in four states on Monday.

But local authorities surveyed by Reuters on Thursday in five states - Ohio, Pennsylvania, Arizona, Wisconsin and Florida - said they were not increasing election-related law enforcement personnel or resources above 2012 levels.

The FBI, which designates one special agent from each of its 56 field offices for election crime matters, has not increased its numbers or given staff additional training this year, said an FBI spokeswoman.

There has been no "substantive change" in the number of personnel deployed by the rest of the Justice Department, which designates Assistant U.S. Attorneys and federal prosecutors within the agency's Public Integrity Section to handle election crimes, according to a spokesman.

Jim Pasco, executive director of the Fraternal Order of Police, which represents hundreds of thousands of U.S. officers, said cops are taking the same security measures they would take for any large event. He said he expects the vows by militias to monitor the polls to be "a lot of talk, little action."

(Additional reporting by Andy Sullivan in Washington; David Ingram in New York; David Schwartz in Phoenix; and Letitia Stein in Tampa, Fla.; Editing by Kevin Drawbaugh and Alistair Bell)