How to migrate runners to another Gitlab instance?

My team is migrating projects from one Gitlab instance to another. The question is:

Is it possible to migrate/export/import the CICD runners? Or do they have to be re-registered, each of them (one by one) in the new Gitlab instance?

I know there is an API to export/import whole projects, so I wonder if there is some similar tool to help the migration of runners.

BR
Emilio