Many groups from India have set up training camps in the southern part of the country. The United Liberation Front of Asom (ULFA), the National Democratic Front of Bodoland (NDFB) and the Bodo Liberation Tigers Force (BLTF) had bases in Bhutan in 2002. Terrorists were involved in murders, extortion and kidnappings. Bhutan told the terrorists they must leave the country by December 2001. In December 2003 there was a military campaign to remove these groups. Many terrorist camps were destroyed. It is thought that terrorists are trying to make retaliatory attacks against Bhutan. On September 5, 2004, a bomb exploded in Gelephu killing two people and injuring twenty seven. The NDFB was suspected behind the attack.