Moscow, 10 September 1999 (RFE/RL) - Russia says security is being tightened at its nuclear power stations due to the growing threat of terrorism. The announcement follows a blast at a Moscow apartment building yesterday that killed at least 84 people. The cause of the explosion is still being investigated. Russia's Deputy Atomic Energy Minister, Yevgeny Fyodorov, told Echo Moscow radio that security around nuclear installations is being strengthened. Prime Minister Vladimir Putin earlier approved a plan to bolster security across the country -- notably in Moscow -- during a meeting with security chief Nikolai Patrushev. Moscow Police Chief Nikolai Kulikov says an additional 4,000 officers have been deployed throughout the city following the blast.