MOSCOW - President Vladimir Putin said today the Kremlin was preparing to take preventive action against terrorists, even as a Chechen rebel leader purportedly claimed responsibility for a series of attacks that killed hundreds of people and threatened further violence.

Putin's comments were the highest-level warning yet that Russia could take some sort of pre-emptive action against terror groups in the wake of this month's deadly school hostage-taking in Beslan. Lower-level officials have threatened anti-terror strikes abroad, and it was not immediately clear whether Putin was referring to actions only at home or outside Russia's borders.

"Now in Russia, we are seriously preparing to act preventively against terrorists," Putin said, according to the Interfax news agency. It quoted him as saying that the steps would be "in strict accordance with the law and norms of the constitution, relying on international law."

Recalling the attempts to appease Adolf Hitler in the 1930s, Putin said there could be no "bargaining" with terrorists.

"Every concession leads to a widening of their demands and multiples the losses," Putin was quoted as saying.

"In this war there is no rear or neutral zone, and where terrorists don't meet the necessary resistance, their bases and coordination centers crop up," Putin said.

His speech came the same day that an e-mail attributed to radical Chechen rebel leader Shamil Basayev was posted on a Web site, claiming responsibility for an August explosion at a bus stop outside Moscow, the near-simultaneous bombings of two planes the same night, a suicide bombing outside a Moscow subway station a week later, and the Beslan hostage-taking, which ended in gunfire and explosions.

More than 430 people were killed in the attacks, with some 338 of those deaths coming during the Sept. 1-3 school siege in Beslan.

The e-mail attributed to Basayev and posted today on the Kavkaz-Center Web site said he had sent a letter to Putin proposing "independence (for Chechnya) in exchange for security."

It was impossible to confirm whether the text - signed with Basayev's nom de guerre, "Abdallakh Shamil, Emir of the Riyadus Salikhin Martyrs' Brigade," - on the Web site was genuine. But the site is considered a mouthpiece for Basayev, and his previous claims of responsibility have appeared there.

The letter to Putin said that if Russia withdrew its troops and recognized Chechen independence, Chechnya would neither support nor finance groups fighting Russia, and "we can guarantee that all of Russia's Muslims would refrain from armed methods of struggle against the Russian Federation, at least for 10-15 years, on condition that freedom of religion (as is guaranteed in the Russian Federation) be respected."