Russian authorities said the bomb exploded today on the second carriage of a moving train, some 300 meters from the Paveletskaya station. The area is in the city center, near the Kremlin.
President Vladimir Putin blamed Chechen separatists, although it was unclear whether the blast was the work of a suicide bomber or someone who merely placed a device on the train as it left the station, the Associated Press reported.
Pro-independence Chechen leader Aslan Maskhadov denied any responsibility in the attack.
Archbishop Kondrusiewicz, head of the Archdiocese of the Mother of God in Moscow, told the Vatican agency Fides: "This attacks shows us once more the terrible face of terrorism, which is not justifiable for any reason. All believers, especially all the media, should be convinced of this, in order to do everything possible to dissuade those who are looking for vengeance. No reason justifies terrorism!"
"As believers of all the religions, we must make every effort to promote peace and concord together, remembering that evil can be conquered with good, and that we do not have to fall into the temptation of vengeance," he exhorted.
The archbishop appealed to Catholics to pray for the dead and wounded and their families.