"It's starting again," said Estelle Campos, 30, standing near the Port Royal station on the Left Bank. Clutching her 6- and 12-year-old sons, she said: "It's always the same people who pay."
The bomb was fashioned from a 13-kilo gas canister - the same type of explosive device used in bombings in 1995 that killed eight people and injured 160. Many of the injuries were caused by the nails.
The bomb went off in the fourth carriage of the RER train at 6.05pm, at the height of the rush hour. The Prime Minister, Alain Juppe, who went to the scene, ordered the re-implementation of the nationwide security plan which was in force during last year's wave of attacks. President Chirac described the attack as "barbaric".
Remy Jiemza, 20, a student, said: "I thought immediately about last year's bombings. "There were women crying, people panicked, some fell to the ground, others were bleeding. Everyone was suffocating."
Yesterday's bomb comes within days of Algeria's referendum in which Algerians apparently voted by a large majority for the country's new constitution which outlaws fundamentalist religious groups.
France on alert, page 13