BBC News Online profiles several people named by the Russian authorities as key suspects in the Beslan school siege in North Ossetia in which more than 300 people - including many children - died.
Shamil Basayev: Chechen warlord
The fearsome rebel leader, 39, has long threatened a series of "kamikaze" attacks inside Russia, arguing that Russian civilians were legitimate targets.
Basayev led the first Chechen mass hostage-taking inside Russia
North Ossetian interior ministry spokesman Ismel Chaov has said: "You can assume it was Basayev, because Basayev is behind most of the terrorist acts."
Shamil Basayev led the first Chechen mass hostage-taking in the southern Russian town of Budyonnovsk in 1995 and he claimed to have organised the seizing of a Moscow theatre in 2002, during which 129 people died.
He is believed to have been behind a stadium bomb attack in Chechnya's capital, Grozny, on 9 May that killed Moscow-backed Chechen President Akhmad Kadyrov.
Most recently, Mr Basayev is said to have organised a series of attacks on government buildings and police stations in neighbouring Ingushetia in June, which left almost 100 people dead.
He has also boasted to have trained Chechen female suicide bombers - the infamous "Black Widows" brigade.
He is also suspected of having links with al-Qaeda operatives.
Moscow-educated Mr Basayev first rose to prominence shortly after Russian forces invaded Chechnya in 1994, when he became one of the leading commanders of the Chechen guerrillas.
"Russia is the last empire: it is built on blood," he said during a BBC interview several years ago.
When Russia was forced to withdraw its forces after the first Chechen war ended in 1996, Mr Basayev stood for president, but came second to the winner, Aslan Maskhadov, now the official Chechen rebel leader.
Mr Basayev also served briefly as prime minister in the self-proclaimed independent Chechen republic of Ichkeria in 1997.
Magomet Yevloyev: Ethnic Ingush rebel commander
Russian security service officials believe that Magomet "Magas" Yevloyev was one of the key organisers of the operation in Beslan, Russian news agencies reported.
Mr Yevloyev - an ethnic Ingush field commander with Chechen rebels - is said to have acted on direct orders from Basayev.
Together with Mr Basayev, Mr Yevloyev was blamed for the 22 June raids in Ingushetia and also for attacks in Dagestan in 1999.
Russian security officials believe that Mr Yevloyev has been responsible for financing and organising attacks across the region, and was also behind a number of kidnappings for ransom there.
Mr Yevloyev's body was allegedly identified by one of the hostage-takers, Russia's Kommersant newspaper reported.
But this has not been confirmed by investigators.
Doku Umarov: Rebel commander of the "south-western front"
Influential Chechen warlord Doku Umarov is believed to have directly led the hostage-taking operation in Beslan, according to the Russian Izvestiya newspaper.
The 40-year-old rebel - who has a reputation of being an enforcer of Basayev's most notorious attacks - was allegedly later recognised by several hostages, who said he was the only one of the attackers not to wear a mask.
In 2002, he became the commander of the "south-western front" of the rebel armed forces, and is believed to have about 1,000 fighters under his command.
Mr Umarov is said to have directly led the June Ingushetia raids.
He is suspected of being behind a string of kidnappings in Chechnya for ransom, and is said by Russian officials to have been involved in killing Chechens cooperating with the Kremlin-backed government.
Mr Umarov also served as Chechnya's security minister during its short-lived independence.
Vladimir Khodov: Alleged fighter in Basayev's brigade
Vladimir "Abdullah" Khodov from North Ossetia is believed to have been a key member of the gang that seized the school, Russian officials say.
Mr Khodov - who hails from the village of Elkhotovo - is suspected of being a fighter in Basayev's brigade and had been on the regional most wanted list after the Ingushetia attacks, the Kommersant reported.
Mr Khodov's body was allegedly identified by one of the hostage-takers, the newspaper said.
It added that Mr Khodov was also wanted for alleged rape in 2000 in Astrakhan region, southern Russia.
Abu Omar as-Seif: Suspected al-Qaeda operative in Chechnya
Russia's Federal Security Service (FSB) officials allege that the hostage-taking raid was financed by Abu Omar as-Seif, whom they describe as al-Qaeda's representative in Chechnya.
"Abu Omar as-Seif, a Wahhabi ideologist, sponsored the hostage crisis in Beslan," a source in Russia's southern federal district secret services told the Itar-Tass news agency.
The source said Mr as-Seif was in charge of distributing the terror group's foreign funds to Chechen rebels.
Russian officials also initially claimed there were up to 10 Arabs among the attackers. However, several surviving hostages have said they saw no Arabs in the school.
But some experts have cast doubt on such claims, saying that the attack could have been the work of any one of a plethora of radical militant groups in the region.