Seoul, Nov 6 : North Korea has successfully built the world's strongest nuclear force under the guidance of its leader Kim Jong-un, as the secretive regime has been bolstering the development of its nuclear and missile programs, Pyongyang's state media said on Monday. The claim came amid speculation that the North is in the final stage of its preparations to make a third attempt to launch a military spy satellite following two failed attempts in May and August, respectivel . "With the power of the revolutionary industry of the ruling Workers' Party of Korea, the country's nuclear force has sharply increased and firmly reached the world's strongest level," Yonhap News agency quoted Tong Thae-gwan, an editorial writer of the Rodong Sinmun -- the North's main newspaper -- as saying in an editorial piece. In a bid to tout Kim's achievements for this year, he cited the North's major provocations and events, such as the test-firing of Hwasong-type intercontinental ballistic missiles (ICBMs) and the summit between the North's leader and Russian President Vladimir Putin in September in Russia's Far East. On Sunday, North Korea had announced that it designated November 18 as a "missile industry day" to celebrate last year's successful launch of the Hwasong-17 ICBM. /IANS