How to set up redirects when a city acts as a dynamic route in Next Js?

Question

React

There is a list of cities of presence ["mks", "spb"]

The project uses a dynamic route [city] - https://nextjs.org/docs/routing/dynamic-routes

- [city]
-- posts
-- news

how to correctly set up redirects from posts, news pages if the city in the url is not valid?
examples

/news -> mks/news
/news/2 -> mks/news/2
/no-page -> /404