Russia has launched one of the biggest security operations in Olympic history, a month before the start of the winter games in the Black Sea resort of Sochi. The authorities are deploying more than 30,000 police and interior ministry troops and limiting access to the area. The main concern is the threat of attack by Islamist militants from the restive North Caucasus region. Russia's most wanted man, Chechen rebel leader Doku Umarov, has urged his fighters to target the Winter Olympics. The BBC's Steven Rosenberg in Moscow says recent deadly bombings in Volgograd have intensified those worries. President Vladimir Putin was in Sochi on Monday night to celebrate the Orthodox Christmas, appearing at a church service. ‘Starting 7 January, all divisions responsible for ensuring the guests' security at the Games are being put on combat alert,’ Emergency Situations Minister Vladimir Puchkov said.