A US Army sentinel guarding the Tomb of the Unknown Soldier appeared to rebuke Defence Secretary Pete Hegseth’s delegation on Wednesday after laughter could be heard as they climbed the steps of the solemn site, according to a video of the incident.

Hegseth, his wife and senior aides could be seen taking pictures and speaking to each other on the steps of the memorial at Arlington National Cemetery following a Veterans Day event.

Immediately after the laughter, the sentinel moved toward the group and, from a distance, shouted toward them: “All visitors will maintain an atmosphere of silence and respect at all times.”

Sitting at the heart of Arlington National Cemetery, the Tomb of the Unknown Soldier is a sacred site and the grave of three unknown American service members, including one from World War One. It is widely known as a place for mourning and for reflection on military service, and sentinels guard the site 24 hours a day.

Asked about the incident, which was first reported by CNN, chief Pentagon spokesperson Sean Parnell said in a statement: “The secretary and the entire department have always honoured and will always honour the sacrifices our military men and women have made to keep America safe.

“While commemorating this solemn day, a soldier correctly and respectfully reminded everyone to maintain decorum.”

Hegseth, a former Army National Guard soldier who served in Iraq, prevailed this week after the House of Representatives rejected a Republican lawmaker’s effort to impeach him.

At a rare Pentagon press conference on Tuesday hours before the vote, Hegseth called the impeachment effort a farce and defended his record, which includes championing the unpopular war on Iran, launching strikes on suspected drug vessels in Latin American waters and firing senior military officers.

Democrats who won control of both chambers of Congress last week have promised to investigate Hegseth for his stewardship of the US military and have not ruled out another impeachment effort.