"We will identify all terrorists linked to this attack ... A large part of this network has already been arrested," the judiciary's news agency Mizan cited Alavi as saying.
The minister did not provide any details about the identity of those arrested or their affiliation, but vowed tough measures against those committing "such crimes," Radio Farda reported.
Gunmen opened fire at Revolutionary Guard troops and officials in Ahvaz at 09:00 local time (06:30 BST). At least 29 people were killed, 57 more were injured.
