A grave Alain Juppe told the National Assembly yesterday afternoon that France would "not allow itself to be intimidated" and would "not capitulate in the face of barbarism". The Prime Minister said that a meeting planned between President Jacques Chirac and the Algerian president, Liamine Zeroual, in New York was for France to "express its point of view". It did not, he said, "imply support for one or another candidate" in Algeria's coming presidential elections.
Mr Chirac, who cut short an engagement in Tours to visit some of the injured in hospital, expressed his horror at the latest attack and condemned those who "resort to fanaticism".
The device exploded on a suburban train close to the Foreign Ministry at the Quai d'Orsay, blowing the feet and legs off some of the victims. A police spokesman said it was a miracle more people were not hurt. After the blast, hundreds of passengers had to walk through a smoke-filled tunnel to safety.
Well-rehearsed emergency procedures had doctors and firefighters at the scene within minutes. A field hospital was set up at Orsay Museum station, where at least one person had a limb amputated.
The explosion was the most destructive in terms of casualties since the first in the current wave of bomb attacks at Saint-Michel station on 25 July. In terms of government and public reaction, it could prove more calamitous. Where the first bomb provoked defiance and stoicism, the eighth seemed to threaten national morale.
Mr Juppe's tone, the immediate visits made to the bedsides of the injured by Mr Chirac, and the unusually solemn faces of people on the streets of Paris yesterday all testified to the fact that this explosion could not be shrugged off.
In the first place, it confirmed that the bomb attacks did not end with the life of Khaled Kelkal, the young Algerian who was shot dead near Lyons two weeks ago. Everyone had suspected as much after the bomb at Maison Blanche metro station in Paris on the day of his funeral. But they had hoped that that bomb, which injured seven people, was a last expression of vengeful hurt, arranged perhaps by his friends.
That is clearly not so. The optimistic statement made by the Interior Minister, Jean-Louis Debre, on the day after Kelkal's death, that he "had a feeling" Kelkal's cell was responsible for all the summer bombs, and by implication, that the attacks were over, now looks even less substantial than it did at the time.
The fact that Kelkal's central role can no longer be assumed will cast the spotlight back on the authorities and their conduct of the investigation. So far, they have apprehended only four people. Kelkal was shot dead by police; his closest companion is still in hospital after the gun battle with police when he covered Kelkal's escape. Two others who were taking supplies to their forest hide-out were arrested at the same time.
A fifth man, Abdelkarim Deneche, is in custody in Sweden, awaiting deportation, but the Swedes have confirmed his alibi for the day of the Saint-Michel bombing and France's grounds for demanding his extradition look shaky as a result.
The authorities have put vast efforts into the investigation. The whole country is on special security alert; army detachments, helicopters and heatseeking cameras were all deployed in pursuit of Kelkal alone. But he and the other three were only tracked down because a man picking mushrooms stumbled upon them.
Further, if Kelkal's involvement seems less crucial than it first appeared, the questions already being asked about the manner of his death will seem more urgent. Initially, the questions were more in the way of regret that he had not been captured alive. But the police and finally the Prime Minister himself all agreed that the gendarmes had had no alternative: Kelkal would not stop firing; they shot in self-defence.
It emerged subsequently, however, that one sequence of film had been excised. It showed Kelkal shouting "Stop, stop" after he was wounded, and apparently raising his hands.
The television company, M6, has acknowledged that the film exists and the ministers, if not the police, knew of it before they made their statements. The post mortem on Kelkal showed that he had been shot 11 times.
But even if the questions about Kelkal's death fade away unanswered, more general questions will remain, especially if a young man held after yesterday's attack - and later released - proves, like Kelkal, to be a child of the run-down micro-cities where many North African immigrants live. Kelkal, it is clear, was not an isolated case. One part of France - sophisticated, prosperous, well-housed, employed, and largely white - now feels threatened by another part of France, by young men of Arab origin, educated if not born in France, who have rejected a country they feel has rejected them and find solace in Islam.
After questions were asked about the showing on television of Kelkal's killing, the head of the independent broadcasting commission, Herve Bourges, made a statement that has since become notorious for summing up this French divide. "You have to remember," he said, "that it was not only our compatriots who were watching television that night, but also the young people of the suburban housing estates." In other words, there are French "compatriots" and they do not include the young of the housing estates, even if they are French citizens.
The final aspect of yesterday's bomb, which will be the most immediately worrying to the French government, is the political message that it conveys.
The target was not chosen at random. It was a train travelling between Saint-Michel, the site of the first explosion, and Quai d'Orsay, next to the French Foreign Ministry.
In acknowledging responsibility for the attacks two weeks ago, a statement from the Armed Islamic Group, the most extreme of Algeria's fundamentalist terrorist groups, said they were directed against French support for the military government in Algeria.