An explosion targeting a bus carrying workers to Russia's main military base in its turbulent Chechnya region on Friday killed three people and wounded eight, security sources in the region said. The attack in a region gripped by a decade of conflict came as heads of state began arriving in St Petersburg, at the other end of the country, for celebrations marking the 300th birthday of Russia's second city, hosted by President Vladimir Putin. The sources said the bus was taking about 20 workers to Khankala, the main Russian military base just outside the Chechen capital Grozny and had dropped them off when the explosion occurred. One person traveling in a nearby car died, along with two others in the vicinity. The bus driver was among the wounded. Interfax news agency quoted Grozny Mayor Oleg Zhidkov as calling for more mobile patrols in the capital but he opposed any increase in Russian forces or restrictions on residents' movements. "We don't need more troops or tougher measures. Setting up barbed wire won't work either," he was quoted as saying. "What we do need is more vigilance by security forces." Putin has refused to speak to Chechen leaders and answered Western critics of two post-Soviet military campaigns by offering Chechnya autonomy. Results of a March referendum showed considerable support for keeping the region in Russia and elections are planned for a regional president and assembly. With rare exceptions, Western countries have toned down allegations of abuse by the Russian military since Russia gave its full backing to the U.S.-led anti-terror campaign after the September 11, 2001, airline attacks. Chechen fighters have rejected the plan and vowed to pursue their fight against Russian rule. Recent incidents have included two bomb attacks last month which killed more than 70 people. **PHOTO CAPTION*** The town of Znamenskoye May 12, 2003, after a truck packed with explosives detonated. (REUTERS/RTR television)