An arms factory was broken into overnight.
Police said the trespassers caused "extensive damage" at EDO MBM Technology in Moulsecoomb.
They were called at 1.50am today.
A spokesman for Sussex Police said: "A number of arrests have been made and inquiries are continuing."
The factory has been the focus of regular demonstrations since 2004 by the Smash EDO group, which aims to close the factory down.
The campaigners claim the firm makes components used by Israel in its conflict in Gaza.
Two protests last year ended in violent confrontations with the police.
Police are asking anyone who saw anything suspicious at the factory in Home Farm Road, Moulsecoomb, this morning is asked to call Sussex Police quoting Operation Potato on 0845 6070999 or Crimestoppers anonymously on 0800 555111.