The New York Police Department has marked the upcoming 15th anniversary of the World Trade Center attacks with a parade to honor the 23 officers it lost on Sept. 11, 2001.

Friday's parade through lower Manhattan also commemorated the 99 officers who have died of illnesses linked to the terrorist attacks.

Police departments from around the United States and Canada joined New York City officials for the parade and memorial ceremony.

Bagpipers led the procession around the southern tip of Manhattan, ending near the memorial wall engraved with the names of the NYPD officers killed in the terror attacks.

Police Commissioner William Bratton thanked the other police departments for their support. Mayor Bill de Blasio, a Democrat, also attended.

The main Sept. 11 memorial ceremony will take place Sunday.