Japan tested a ballistic missile defense unit in the center of Tokyo on Tuesday, stepping up preparations to secure the capital from what is seen as an increased threat from neighboring North Korea. The drill at the Defense Ministry headquarters in Tokyo involved land-to-air PAC-3 Patriot interceptors, Defense Minister Shigeru Ishiba said during a regular news conference. «We are not deploying PAC-3 just for fun, » Ishiba was quoted as saying by the Associated Press. «We have to make sure its capability is truly reliable and the personnel in charge of it are well trained. » About 250 Ground Self-Defense Forces soldiers participated in Tuesday's drill, the first full-fledged exercise using the PAC-3 unit that Japan deployed last year. The exercise was designed to test the troops' ability to use the equipment efficiently and safely, a ministry spokeswoman said on condition of anonymity, citing department policy. Kyodo News agency said the soldiers used training ammunition and adjusted the angle of the missile launcher, along with checking radio signals. Tokyo and Washington have accelerated a joint missile defense program following North Korea's missile and nuclear tests in 2006. The surface-to-air Patriots would be used as a last defense in case interceptors fired from U.S. or Japanese warships fail to knock out incoming missiles.