It's pronounced like "Turk", but with the 't' left off. I can see how this is a point of the utmost importance for making a decision, so I'm glad my being a native speaker of Dutch has finally come in useful!
Have to share..
Urk is an existing live concerttour of a band called “The Nits”. It is published as a cd in 1989.
It is worth while to give it and them a listen. link