The Chechen rebel leader who claimed responsibility for the Beslan school massacre and the Moscow theatre siege has been killed, Russian media reported today.

Russia's Itar-Tass news agency reported that Shamil Basayev, who led the most violent wing of the Chechen separatist movement, had been killed overnight in the Russian republic of Ingushetia, to the west of Chechnya.

The Russian president, Vladimir Putin, was quoted as saying that Basayev's killing was "deserved retribution" for terror attacks carried out by his group.

Itar-Tass also quoted the head of Russia's FSB intelligence service saying that Basayev had intended to "put political pressure on the Russian leadership" during the summit of the G8 nations scheduled for this week in St Petersburg.

The remarks appear to allude to plans of a terrorist attack during the meeting, which is due to begin on Saturday.

Basayev was the most feared of all Chechen terrorist leaders, and relished his image as a ruthless and brutal killer.

His is the most significant scalp to have been claimed by Russian forces in their fight against Chechen separatists.

Alu Alkhanov, the president of Chechnya's Kremlin-backed government, said Basayev's death would be a major step forward in the attempt to suppress the Chechen insurgency.

"I consider that today can be considered the date of the logical end of the fight against illegal armed formations," he told Interfax news agency.

Russian forces have killed several prominent Chechen leaders since the assassination of the separatist president Aslan Maskhadov last year.

Last month, Maskhadov's successor, Abdul-Khalim Sadulayev, was killed and his bloodied body displayed after he was betrayed by one of his lieutenants in exchange for money to buy heroin, according to Russian officials.

But Basayev was more feared than either of those men, who were both mainly political rather than military figures.

His characteristic operation was the hostage siege, but his troops were also feared for suicide bombings and more conventional operations.

The 41-year-old first rose to prominence during the first Chechen civil war in the mid-1990s as commander of a battalion of 2,000 fighters who fought running battles with Russian troops in the battle for the Chechen capital Grozny.

Following the failure of the Chechen military campaign, Basayev ordered the invasion of a hospital in the Russian town of Budyonnovsk and held around 1,600 people hostage until the siege was broken, with the deaths of 129 people.

After losing the 1996 Chechen presidential election to the more moderate Maskhadov he was briefly appointed Chechen prime minister in 1998, but returned to guerrilla warfare the following year as the Russian military won back more control over Chechen territory.

Hundreds of civilians have been killed in more than a dozen operations for which he has claimed responsibility since then, most notoriously the 2002 Moscow theatre siege and the 2004 Beslan high school siege.

The former incident resulted in more than 170 deaths after Russian security forces attempted to knock out the hostage-takers with gas, poisoning many of the people they had intended to save.

The Beslan siege ended even more bloodily, with 350 people killed when Russian special forces opened fire on one of the hostage-takers and the terrorists detonated bombs surrounding the children and teachers they had kidnapped.

Basayev justified his actions by pointing to Russia's brutal occupation of Chechnya, which is thought to have resulted in more than 200,000 deaths of Chechen civilians and military personnel. He described the ongoing Russian occupation as "genocide".

"I admit, I'm a bad guy, a bandit, a terrorist ... but what would you call [the Russians]?" he said in an interview with ABC News last year. "If they are the keepers of constitutional order, if they are anti-terrorists, then I spit on all these agreements and nice words."