The Russian President, Vladimir Putin, has said he has ordered his security forces to draw up new plans for dealing with international terrorism.
Speaking on television, Mr Putin said terrorists were becoming bolder and were threatening to use methods comparable to weapons of mass destruction.
He said Russia would take what he called appropriate measures against terrorists wherever they were.
He warned that Russia would make no deals with terrorists and would not give in to any form of blackmail.
Mr Putin's comments came on a day of national mourning for the hostages who died in the Moscow theatre siege.
117 hostages, together with 50 Chechen rebels who were holding them captive, died after Russian troops stormed the building on Saturday.
More than 600 others remain in hospital, some of them in a critical condition.
While Moscow maintained a wall of silence around the precise nature of the gas, a top medical official said "sarin or other poison gases" were not used, but rather an "anesthetising gas used in surgery."
The President is now facing growing criticism from his political opponents over the pumping of gas into the theatre.
Urging President Putin to agree to peace negotiations, Chechen rebel leader Aslan Maskhadov warned that more attacks like the brutal Moscow hostage-taking were inevitable unless a political solution was found.A member of the opposition Liberal Democratic Party, Alexei Mitrafanov, said the real problem highlighted by the disaster was the lack of openness in government.
