The US homeland security chief said Friday authorities have confidence in the integrity of electoral systems despite growing cybersecurity threats.

Department of Homeland Security Secretary Jeh Johnson offered his agency's assistance to state and local election authorities in protecting voting systems.

Johnson's comments come amid reports of cyberattacks on Democratic Party systems and on voter databases in some jurisdictions. Some reports have said Russia may be behind some attacks, although US officials have not confirmed this.

"In recent months, we have seen cyberintrusions involving political institutions and personal communications," Johnson said in a statement.

"We have also seen some efforts at cyberintrusions of voter registration data maintained in state election systems. We have confidence in the overall integrity of our electoral systems. It is diverse, subject to local control, and has many checks and balance built in."

Nonetheless, Johnson added that "we must face the reality that cyberintrusions and attacks in this country are increasingly sophisticated, from a range of increasingly capable actors that include nation-states, cyber hacktivists, and criminals. In this environment, we must be vigilant."

The Department of Homeland Security "stands ready to assist state and local election officials in protecting their systems" as it does for private businesses and other organizations, he added.

He noted that DHS does not take over systems or regulate them but can offer "cyber hygiene scans" and other tools to help identify vulnerabilities.

DHS also will publish "best practices" for securing voter registration databases and addressing potential threats to election systems from ransomware.

"In recent weeks, a number of states have reached out to us with questions or for assistance," he said. "We strongly encourage more state and local election officials to do so."