Americans are marking 24 years since the Sept. 11, 2001, attacks with solemn ceremonies, volunteer work and other tributes honoring the victims.

Axar.az informs, citing AP, many loved ones of the nearly 3,000 people killed will join dignitaries and politicians at commemorations Thursday in New York, at the Pentagon and in Shanksville, Pennsylvania.

Others choose to mark the day at more intimate gatherings.

The remembrances are being held during a time of increased political tensions. The 9/11 anniversary, often promoted as a day of national unity, comes a day after conservative activist Charlie Kirk was shot and killed while speaking at a college in Utah.

Kirk’s killing is expected to prompt additional security measures around the 9/11 anniversary ceremony at the World Trade Center site in New York, authorities said.