This is not in Belgium, but in Béthune, France, although not far from the Belgian border.
The belfry (the tower) is originally from 1346, but was destroyed during the first world war and rebuilt between 1921 and 1923. You can find it on Google Streetview from almost the same point as your photographs have been taken.
Image source: Wikimedia Commons
How did I find it? Since the time period matches, I assumed that the tower was being rebuilt after the first world war and googling for images of belfries rebuilt after the first world war returned a picture of this tower as one of the first hits.
Credit:stackoverflow.com‘