The explosions and gunfire that have rocked the former Soviet republic of Uzbekistan this week dramatically raised fears of an onslaught of regional terrorism that could send tremors as far as Washington and Moscow

Both the United States and Russia regard the countries of Central Asia as vital security interests and watched with alarm as Uzbekistan was gripped by suicide bombings and police shootouts with apparent Islamic extremists, in which more than 40 people have died since Sunday. The United States places high importance on stability in the oil-rich region, which borders Russia, Afghanistan and Iran, especially since the Sept. 11, 2001, terror attacks. U.S.-led coalition forces are using bases in Uzbekistan, Kyrgyzstan and Tajikistan to help fight against Taliban and al-Qaida insurgents in Afghanistan. Russia opened its own air base in Kyrgyzstan in what was seen as a response to the American presence. Washington also hopes that Kazakhstan and Turkmenistan will become reliable suppliers of oil from the rich Caspian Sea fields, potentially reducing Western dependence on oil from the turbulent Middle East. But the United States also considers Central Asia a potential breeding ground for Islamic extremism and a possible marketplace for nuclear or dirty bomb components. Central Asia has a more immediate impact on Russia's security. It provides gas and oil that heat many Russians' homes and flow through its lucrative pipelines. The region also is a virtual pipeline for illegal immigrants and drug traffickers toting Afghan heroin, heading to Russia or Western Europe. Growing instability would undermine efforts to stem these flows.