The parents of Israeli soldier Gilad Shalit, captured by Palestinian militants in Gaza in 2006, on Monday filed suit in a Paris court against his kidnapping and illegal imprisonment.
The complaint by the parents of Shalit, who also has French citizenship, states that the kidnap was accompanied by aggravating circumstances and that he may have "suffered from acts of torture or of barbarism."
The suit, brought by Noam and Aviva Shalit, is being taken against persons unknown but clearly identifies the Palestinian Islamist group Hamas as the alleged kidnapper of the young soldier.
The militia, which took control of Gaza a year after Shalit's capture, has demanded the return of hundreds of prisoners in exchange for his release, including scores of militants responsible for deadly anti-Israeli attacks.
Shalit, now 24, was seized in a 2006 dawn cross-border raid by militants from three Palestinian groups, including Hamas.
The last sign of life received from his captors was in October 2009 when a video recording showed him looking gaunt but apparently in good health.
French foreign minister Alain Juppe met last week with Shalit's parents in Jerusalem and assured them that France was determined to do all it could to secure his release.
Negotiations for his release have stalled, with Israeli Prime Minister Benjamin Netanyahu warning that Palestinian militants released in previous prisoner exchanges have gone on to launch deadly attacks on Israel.
Netanyahu has come under increasing criticism for his government's failure to secure Shalit's release in talks, which have been mediated by Germany.