Move follows army chief's pledge to launch anti-fraud crackdown as protesters continue to demand political overhaul.
The four are being held in connection with a corruption investigation, state TV says.
Protesters reject army bid to remove president on health reasons, call it attempt by old guard to maintain status quo.
Probabilmente é la più grande dall' inizio delle proteste
Police use water cannon and tear gas as protesters demand the resignation of President Bouteflika.
Army chief Ahmed Gaid Salah says 82-year-old president is so ill he should be declared unfit to rule.
Opposition leaders say general's call for Bouteflika to be declared unfit to rule is a manoeuvre to preserve old guard.
Consiglio costituzionale ha rigettato le uniche due candidature
The presidential election scheduled to be held on July 4 cancelled - a move protesters have been demanding for weeks.
Ahmed Gaid Salah calls for a constitutional procedure that would see the president's removal on health grounds.