The department did not cite a specific threat but pointed to "a heightened threat environment across the United States" that it believes "will persist" in the weeks since Biden took office.

DHS said it consulted with law enforcement and intelligence agencies before issuing the alert about the potential for homegrown violent extremism.

"Information suggests that some ideologically-motivated violent extremists with objections to the exercise of governmental authority and the presidential transition as well as other perceived grievances fuelled by false narratives, could continue to mobilise to incite or commit violence," the bulletin said.

With the warning, the Biden administration is effectively stepping into the politically charged debate over how to describe or characterise acts motivated by political ideology, suggesting that it sees violence aimed at overturning the election as akin to terrorism.

The alert comes at a tense time after the January 6 riot at the Capitol by a group of supporters of then-president Donald Trump who were seeking to overturn the presidential election.

Some domestic violent extremists "may be emboldened" by that siege, according to the bulletin.

DHS also notes violent riots in "recent days," an apparent reference to events in Portland, Oregon, linked to anarchist groups.

The alert was issued by acting Homeland Security Secretary David Pekoske.

Biden's nominee for the cabinet post, Alejandro Mayorkas, has not been confirmed by the Senate.

Australian Associated Press