Fire department sirens have sounded across the Argentine capital to honor 85 people who died 25 years ago in the nation's worst terrorist attack – the bombing of a Jewish center.
Argentine prosecutors blame Iranian officials for plotting the attack on the Argentine-Israelite Mutual Association and say the Lebanese Shiite group Hezbollah carried it out. But nobody has been convicted despite years of investigations.
Earlier attempts at prosecutions collapsed. Iran has refused to turn over the people who now face charges, and denies any involvement.
Prosecutor Alberto Nisman in 2015 accused former President Cristina Fernandez of helping cover up the case, which she denies. Nisman was found dead in his apartment days later.
U.S. Secretary of State Mike Pompeo is to attend a memorial service on Friday.