The traditional wreath-laying at the Co Tyrone town’s war memorial also had to be postponed because police were dealing with a suspicious device and sealed the area off.
Chief constable George Hamilton said it was being examined to determine if it was viable.
“The disruption of the Remembrance Day parade and service in Omagh this morning was just sickening, actually.
“Deeply disrespectful, hard to believe that some people are so still stuck in the past, in Omagh of all places - the trauma and the pain that town and the families of Omagh have been through.”
A dissident republican Real IRA blast killed 29 in the busy market town in 1998.
It was one of the bloodiest killings of a conflict which lasted for 30 years and happened months after the Good Friday Agreement which largely ended violence.
Mr Hamilton said: “There has been some form of interruption this morning, to people in a dignified way wanting to pay their respects and to remember those who have been sacrificed.”
One of his officers said those behind the suspected device were cowards.
Chief inspector Graham Dodds said: “This is a sickening attempt by cowards to create fear and disruption on a day when many gather to pay their respects to the brave men and women who paid the ultimate sacrifice, and must be unreservedly condemned.”