9/11: Nicola Sturgeon pays tribute to victims of September 11 attacks
The First Minister posted on Twitter: "No-one old enough to remember will ever forget where they were, and the sense of utter disbelief, as the horror of 9/11 unfolded.
"20 years on, my thoughts are with all the victims of those horrific terror attacks - those who died and those left behind to grieve."
She included a photo of the 9/11 Memorial at the site of the attack on the World Trade Centre twin towers in New York City.
Firefighters across Scotland will be among those paying their respects on the anniversary.
The Scottish Fire and Rescue Service plans to lower station flags and hold a one-minute silence.
The service posted on Twitter: "Today marks 20 years since the 9/11 attacks.
"Station flags will be lowered and SFRS staff will stop at 1.46pm for a one-minute silence to show our support to @FDNY and pay respects to all those who lost their lives."