It'll be interesting to see if he actually tries to take control of any of the companies, I'm not sure of the ruling in Turkey but in the US if they buy more than 5% they have disclose if they intend to acquire.
Can you be prevented from buying more stock if you say you do intend to acquire? As in, can the company tell you flat-out to stop buying, because of course they can always raise the price or sell to someone else, etc.
If you intend to acquire then at some point you might have to make a tender offer.