Further excerpts from the declaration give a flavour of the febrile state of mind of its author:
“We, the autonomous military group Combat 18, claim responsibility for the “Nevskii Express” explosion. Further – greater! The time has come. We declare that the war will touch every resident. In this war there will be no non-participants and no innocent victims. There will only be our supporters and our enemies.” That anyone or any group claiming to be of a Russian nationalist persuasion should choose to indiscriminately kill its own people seems bizarre, and would seem to call into question the credibility of the claim. Is it the product of a lone crank, or of the small dangerously deluded group of which he claims to be a member? Whoever this person is, he is no friend to the Russian people.
The idea that this act could have been carried out by anyone claiming to be a Russian nationalist has been roundly rejected by Aleksandr Belov, leader of Russia’s Movement Against Illegal Immigration. In an interview with Novyi Region Moskva, he argues that it is likely to have been carried out by Chechen terrorists, rather than by some shadowy group of violent ultranationalist cranks.
In support of his view Belov notes that: 1) articles have already appeared on a number of Chechen websites claiming responsibility for the bombing; 2) a trial of Chechen terrorists charged with an earlier bombing of this train service in 2007 is currently underway; 3) the attack coincided with the start of Eid al-Fitr . As Belov notes, there thus appears to be ample circumstantial evidence to identify the likely suspects as Chechen Islamists. Alas, this is but the latest in a long sequence of Chechen terrorist atrocities endured by the Russian people, and I fear that it will not be the last.
References:  Cited in http://www.gazeta.ru/politics/2009/11/28_a_3292177.shtml
 Cited in http://www.nr2.com.ua/moskow/259087.html