PORT-AU-PRINCE—Four former Haitian political prisoners filed suit Wednesday for violation of their human rights against former dictator Jean-Claude "Baby Doc" Duvalier, whose surprise return to Haiti stunned this devastated country and is now stoking old political passions.

The suits could be the beginning of several similar legal actions and indicate that Mr. Duvalier's legal problems are likely to quickly multiply. On Tuesday, Haiti's chief magistrate formally re-opened a 2008 case charging the former dictator, who was overthrown and went into exile in France in 1986, with crimes including embezzlement of funds, money laundering and murder.

Under Haiti's legal system, the investigating magistrate now has 90 days to either indict Mr. Duvalier, 59, or dismiss the charges.

"It's mind-boggling that a man like Duvalier thinks he can come back after 25 years and nothing will be held against him," said Michel Montas, a prominent former journalist and owner of a radio station here, one of the four Haitians to file a suit against Mr. Duvalier. "Each of us filed a separate claim for arbitrary arrest, detention, torture and forced exile."

Ms. Montas said her case was based on the shutdown of her radio station on November 1980 amid a general crackdown on the Haitian opposition.