The Ealing Studios version of 'Die Hard'
There are some notable similarities between this movie and the 1988 movie if one overlooks the fact that this movie is set in a town, not a skyscraper.
It certainly is one of the earliest 'siege' movies ever made and pretty violent for that era, even with the war going on -- reminds me also of the 1976 war movie "The Eagle Has Landed", the look of which was certainly influenced by this film.