A number of countries and international bodies have imposed sanctions against North Korea. Currently, many sanctions are concerned with North Korea's nuclear weapons program and were imposed after its first nuclear test in 2006. The United States imposed sanctions in the 1950s and tightened them further after international bombings against South Korea by North Korean agents during the 1980s, including the Rangoon bombing and the bombing of Korean Air Flight 858. In 1988, the United States added North Korea to its list of state sponsors of terrorism.