Washington DC - A week after Joe Biden's inauguration, security authorities are still worried about attacks carried out by extremist supporters of former President Donald Trump. A terror bulletin has now been issued nationwide.

According to the New York Times, the US Department of Homeland Security still sees a risk of danger among frustrated people who do not want to accept Biden's election victory.

There are currently no indications of concrete attack plans, but there is talk of a "heightened threat environment."

The department wrote, "some ideologically-motivated violent extremists with objections to the exercise of governmental authority and the presidential transition, as well as other perceived grievances fueled by false narratives, could continue to mobilize to incite or commit violence."

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The department also fears that some extremists could act out of anger over migration policy or coronavirus-related restrictions.

The storming of the US Capitol at the beginning of January could play a decisive role, the report says. Violent extremists may feel emboldened by the events to carry out further attacks on state representatives or government offices.

Shortly after the Capitol riots, US security authorities warned of further attacks, including fears that violent Trump supporters could appear at the Capitol during Biden's inauguration to hunt down US Democrats.

Joe Biden formally took office as US president on January 20, succeeding Trump, who was voted out of office after just one term.