Mr Ri also said the North's nuclear programme is a "precious fruition of the Korean people's bloody struggle for defending the destiny and sovereignty of the country from the protracted nuclear threat of the USA imperialists and a treasured sword of justice".
North Korea is widely expected to conduct another provocation this month, possibly around the Oct 18 opening of the 19th Congress of the Chinese Communist Party.
North Korea has launched two missiles over Japan and conducted its sixth nuclear test in recent weeks as it fast advances towards its goal of developing a nuclear-tipped missile capable of hitting the U.S. mainland.
The vessels are the first to be designated under stepped-up sanctions imposed on North Korea by the 15-member council in August and September over two long-range ballistic missile launches and Pyongyang's sixth and largest nuclear test.
North Korea swore on Wednesday to bring "a hail of fire" after President Trump "lit the wick of war" with the Hermit Kingdom, the latest dramatic pronouncement promising conflict between the rogue regime and the United States. In May the ministry said North Korea had hacked into Seoul's military intranet but did not say what had been leaked.
The regime allegedly breached South Korean defense systems late previous year and stole classified military documents, including allied war plans for a renewed military conflict on the Korean Peninsula and South Korean wartime defense plans.
Accompanied by U.S. Air Force F-15 fighters, the bombers flew the mission more than 200 miles east of the Korean peninsula.More news: "It's a possibility" - Dani Alves speaks about Arsenal's Sanchez joining PSG
It remains unclear whether North Korea is holding official celebrations for the party anniversary or if its leader Kim Jong-Un is making any public appearances for the occasion.
US Air Force Major Patrick Applegate said: "Flying and training at night with our allies in a safe, effective manner is an important capability shared between the US, Japan and the Republic of Korea and hones the tactical prowess of each nations" aviators'.
Trump defended his tough approach on Wednesday as he conceded differences on North Korea with his own top diplomat, Rex Tillerson, who advocates keeping open the possibility of negotiations with Kim's authoritarian government.
To make the complex fully operational again, North Korea would also be hard pressed to replace the electricity supply that came from South Korea, according to the Kaesong business owners.
" "Continuous Bomber Presence" missions ensure the USA, along with key allies, have a credible capability to respond to a variety of levels and types of threats throughout the Indo-Asia-Pacific region", the Air Force statement said.
CNN reported that depending on the level of detail in the stolen plans, the hack could pose serious challenges for the US-South Korean alliance.