The US Capitol Police department has obtained intelligence pointing to a possible plot to "breach the Capitol by an identified militia group" on Thursday.
The agency added that it is working with local, state and federal agencies "to stop any threats to the Capitol," adding, "We are taking the intelligence seriously." No further details on the threat were provided.
Thursday marks the date when some right-wing conspiracy theorists have claimed that former President Donald Trump, who was defeated in the November 3 election, will be sworn in for a second term in office.
A pro-Trump mob that authorities have said included a number of right-wing extremists stormed the Capitol on January 6 and interrupted the formal certification of President Joe Biden's election victory over Trump in a rampage that killed five people including a police officer.
The Capitol Police statement noted that it already has made "significant security upgrades" at the Capitol, home to the US House of Representatives and Senate.
It was unclear if these upgrades were done in response to this latest threat or whether it includes the measures already in place following the January 6 riot.
US National Guard troops patrolling the streets of Washington DC as part of what President Donald Trump said was his crackdown on crime will begin carrying weapons on Sunday night, two officials said.
Israeli strikes hit the Yemeni capital Sanaa on Sunday in retaliation for Houthi missiles fired towards Israel, with a Houthi health official saying the attack killed six people and wounded 86.
Syria's first parliamentary election under its new administration, scheduled for September, will not include the southern province of Sweida and two other provinces due to security concerns, the electoral commission announced.
Ukraine launched a drone attack on Russia on Sunday, forcing a sharp fall in the capacity of a reactor at one of Russia's biggest nuclear power plants and sparking a huge blaze at the major Ust-Luga fuel export terminal, Russian officials said.
Ukrainian President Volodymyr Zelenskyy marked Independence Day on Sunday alongside Canadian Prime Minister Mark Carney, who said Ukraine would receive more than C$1 billion ($723 million) in military aid from a previously announced package next month.
The UAE has sent another round of aid to the Gaza Strip, completing its 79th airdrop in cooperation with Jordan, in an effort to meet the urgent demands of the enclave's residents as they undergo dire humanitarian conditions.