Seoul, June 11 : North Korean leader Kim Jong-un called for stronger "self-defence" measures to tackle "very serious" security challenges as he presided over a key ruling party session earlier this week, Pyongyang's state media reported on Saturday. But there was no specific message issued from the fifth enlarged plenary meeting of the party's eighth Central Committee with regard to the possibility of the secretive regime carrying out another nuclear test, reports Yonhap News Agency. The North stopped short of delivering new major messages toward the US or South Korea through the three-day high-profile session that ended Friday. It instead announced the promotion of Vice Foreign Minister Choe Son-hui, who used to play a key role in denuclearization talks, to the post of foreign minister. Foreign Minister Ri Son-gwon has been tapped to lead the party's United Front Department tasked with handling inter-Korean relations. The North said that the right to self-defence is a matter of protecting national sovereignty, stressing that the security circumstance for the North is "very serious" and at risk of being further aggravated, according to Pyongyang's official Korean Central News Agency (KCNA). He then reaffirmed the principle of "power for power and head-on contest" and urged efforts to accomplish the goal of bolstering national defence capabilities "as soon as possible", the KCNA said. The KCNA did not specify whether Kim made a direct mention of the North's reported plan for another nuclear test. During the party session, the North also focused on the issue of controlling the current Covid-19 outbreak. Kim was quoted as saying that the state anti-epidemic work has currently "entered a new stage" from a blockade-based prevention system to preventing the spread of the virus based on both a lockdown and eradication of the virus. /IANS