By Gilbert Reilhac and Alexandria Sage STRASBOURG/PARIS (Reuters) - An Islamist suspected of a grenade attack on a Jewish market was shot and killed by police in the northeastern city of Strasbourg on Saturday and 11 others detained in what prosecutors called a "vast anti-terrorist operation." Elite police squads carried out simultaneous operations against a network of radical Islamists in the Paris region and in Strasbourg, Nice and Cannes early on Saturday. The raids were connected to a September 19 incident in the Paris suburb of Sarcelles in which two men, including the suspect killed on Saturday, threw a grenade into a Jewish kosher supermarket, wounding one person and causing minor damage, said Paris prosecutor Francois Molins. "A vast anti-terrorist operation was conducted this morning," Molins told a news conference. He named the deceased as French citizen Jeremie Sidney, 33, who he said had spent two years in prison for drug-dealing and belonged to a radical Islamist movement. "Jeremie Sidney appeared to be a delinquent converted to radical Islam who belonged to a group suspected, without certainty, to want to enter into jihad," Molins said. In the worst incident, three Jewish children and a rabbi were among seven people shot dead in March by an al-Qaeda-inspired gunman. Last week, the government said the terrorist threat to France remained high as it presented legislation that would allow police to arrest those believed to have been involved in terrorism-related activity outside French borders. Ten people detained by police, all French, included one of Sidney's two wives - who had been in the apartment with her two young children during the raid - and three with criminal records for drugs, theft and violence, Molins said. One man in the Paris region had just returned from morning prayers and was carrying a "ready to fire" 22-caliber pistol when police arrested him at his home, he said. An eleventh man was arrested on Saturday evening in Cannes, a judicial source told Reuters, calling the suspect "the last person targeted in today's operations." During their searches, police found al Qaeda literature, 27,000 euros ($35,300) in cash, munitions and a list of Israeli associations in Paris at the homes of suspects. DNA from Sidney, the principal target of the raids, had been found on the grenade lobbed into the Jewish market, Molins said. One officer participating in the raid was wounded as the unit entered Sidney's fourth-floor apartment around 6 a.m. (0400 GMT) in the Esplanade district of Strasbourg. "They found themselves in front of an individual who was upright, gun in hand, and who opened fire," Strasbourg prosecutor Patrick Poirret told a press conference. Sidney, who was armed with a .357 Magnum revolver and had reserve ammunition nearby, died in the hallway after being shot by police, he said. The wounded officer's life was not in danger, police said. Poirret said investigators believed Sidney was "very determined to end up as a martyr." President Francois Hollande, who has taken a hard line on crime and security, said in a statement the government would protect citizens "against all forms of terrorist threats." Hollande is caught between wanting to appear tough on crime while holding to campaign promises to help underprivileged immigrant communities where poverty and joblessness have bred alienation and, in some cases according to social workers and police, driven them to radicalism. France is home to the largest population of Muslims in Europe, and in the poor housing estates ringing many French cities, some Muslim residents have expressed anxiety that incidents involving extremists will further complicate relations with police. ($1 = 0.7657 euros) (Additional reporting By Nicolas Bertin and Emmanuel Jarry, Writing by Alexandria Sage; Editing by Myra MacDonald)