President Vladimir Putin declared Saturday that the attack on a school in southern Russia in which more than 340 people were killed was carried out by international terrorists waging a "total, cruel and full-scale war" against the country. He offered a rare acknowledgement of lapses by the security services and vowed not to give in to demands of separatists.

In a 10-minute televised address that was rebroadcast by state-controlled television stations throughout the evening, Putin appealed for a "mobilization of the nation before a common danger." He also said he would take new measures, which he did not detail, to respond to gaps in security and borders exposed by the assault on School No. 1 in the town of Beslan.

Putin did not explicitly mention the war in the separatist region of Chechnya, which borders North Ossetia, where about 1,200 hostages were taken last Wednesday inside the school by Chechen fighters and their allies.

"We showed weakness, and the weak are trampled upon," he said, flanked by a Russian flag and striking a somber tone. "Some want to cut off a juicy morsel from us, while others are helping them."

"We are dealing with direct intervention of international terrorism against Russia, with a total, cruel and full-scale war in which our compatriots die again and again," Putin said. "We cannot but fail to see the obvious. We are dealing here not just with separate actions aimed at frightening us, not just with separate terrorist sorties."

At dawn, Putin visited Beslan, where bodies were still being pulled from the school gym. Putin met with local and federal law enforcement officials, his face drawn and tense as he delivered instructions to block the borders of the region and find all those who participated in the attack. Officials said 26 of the attackers were killed. Before returning to Moscow, Putin also called on a local hospital to offer condolences to victims, but those he visited appeared to be sleeping.

Putin has championed the idea of strengthening the state after the tumult of the 1990s, and has installed officials from the security services in key posts. But in his televised speech, he said the law enforcement authorities had not been ready for the school attack, which appeared to be well organized.

Putin called for a "fundamentally new approach to the actions of the law enforcement agencies" and promised to try to clean up corruption in the judicial and law enforcement systems. The security services have been embarrassed by a string of attacks by the Chechen fighters and their allies in other Russian regions and the capital.

"In these conditions, we simply cannot, we must not live as carelessly as we have done until now," Putin said. "We must create a more effective security system, demand from our law enforcement bodies actions which are appropriate to the level and scale of the new threats that have emerged."

Before the attack, Putin had insisted that the war in Chechnya was over and that the region was returning to normalcy. But the past two weeks have brought a succession of strikes on targets in Russia, including the downing of two airliners and a bombing outside a Moscow subway station.

Putin, a former KGB colonel, suggested that the origins of the larger crisis facing Russia lay in the collapse of the Soviet Union. He said that, "today we are living in conditions which have emerged following the breakup of a vast great state, a state which unfortunately turned out to be unable to survive in the context of a rapidly changing world. But despite all the difficulties, we have managed to preserve the core of the colossus which was the Soviet Union." In the new Russia, he added, "we all expected changes, changes for the better. But we have turned out to be absolutely unprepared for much that has changed in our lives."

"On the whole," he added, "we have to admit that we have failed to recognize the complexity and dangerous nature of the processes taking place in our own country and the world in general. In any case, we have failed to respond to them appropriately." He said Russia was being targeted by terrorists because "as one of the world's major nuclear powers, Russia is still posing a threat to someone, and therefore this threat must be removed."

Putin, who has come to dominate Russian politics and government, as well as national television, said the terrorists were not a challenge to the government alone. "This crime of the terrorists, inhuman, unprecedentedly cruel, is not a challenge to the president, to parliament or to the government," he said. "This is a challenge to the whole of Russia, to the whole of our people; this is an attack on our country."

"The terrorists believe they are stronger than us, that they will intimidate us with their cruelty, that they will be able to paralyze our will and demoralize our society," he said. "And it would appear that we have a choice of resisting them, or agreeing to their claims, surrendering, allowing them to destroy and split Russia, in the hope they will finally leave us in peace."

Putin insisted, "we have no choice." He added, "Because if we allow ourselves to be blackmailed and if we give in to panic, we will submerge millions of people into endless and bloody conflicts," such as the separatist battles fought in recent years in the former Soviet Union. Putin said "the aim of those who sent the bandits to carry out this horrific crime" was to "unleash a fratricidal bloodbath in the North Caucasus." He promised measures to "strengthen the unity of the country," and to better coordinate Russia's forces in the region.