The US Justice Department has created a new position to fight domestic terrorism and extremism in the United States.

Assistant Attorney General John Carlin announced last week that the Justice Department has created the Domestic Terrorism Counsel "to serve as our main point of contact for US Attorneys working on domestic terrorism matters."

He said the new position "will not only help ensure that domestic terrorism cases are properly coordinated, but will also play a key role in our headquarters-level efforts to identify trends to help shape our strategy, and to analyse legal gaps or enhancements required to ensure we can combat these threats."

Carlin said new communications technologies including social media "pose tremendous challenges to public safety and national security and these are challenges everyone with a stake in the matter must continue to work together to address."

The same is true for domestic terrorism and extremism, he said.

"Sovereign citizens continue to communicate and recruit through the use of YouTube and Twitter. White supremacists post to social media, and studies now posit that mass killings are contagious. Violence begets violence, and through the power of the Internet, a meeting hall is no longer needed. Formal organisational structures are unnecessary. Connections are made, and messages spread, through the push of a button," he said.

He said the aim is to disrupt and prevent attacks.

"We do not investigate people for exercising their First Amendment rights, but we are obligated to investigate extremist groups and individuals when we have reason to believe they may be involved in the commission of a federal crime, including threatening violence," he said.

John Whitehead of the Rutherford Institute said, "The legal gaps are probably laws that need to be changed," according to WND.com.

"I'm sure it's gun laws," said Tom Fitton, president of Judicial Watch, another watchdog agency.

Carlin said the "line between speech and violence is crossed too often, resulting in heartbreaking tragedy" including plots and attacks on government buildings, synagogues and mosques, businesses and public infrastructure; assassinations and planned assassinations of police officers, judges, civil rights figures, doctors and others; stockpiles of illegal weapons, explosives and biological and chemical weapons; and killing sprees that have terrorised local communities.

"Looking back over the past few years, it is clear that domestic terrorists and homegrown violent extremists remain a real and present danger to the United States. We recognise that, over the past few years, more people have died in this country in attacks by domestic extremists than in attacks associated with international terrorist groups," he said.

Carlin said "racial hatred motivates many of the violent extremist attacks," citing Charleston shooter Dylann Roof.

Fitton said President Obama's legacy includes targeting conservatives.

"This administration takes a dim view of conservatives and one memo indicated membership in many mainstream conservative organisations was incompatible with military service," Fitton said. "Ironically, it's probably the Justice Department itself that has done the most to foment racial violence in America over the last year or two."