North Korea's state media marked the nation's 69th founding anniversary on Saturday with calls for a nuclear arms build-up, in defiance of mounting international sanctions.
South Korea's military said it was keeping a close watch on the North amid speculation it could stage a missile launch or another nuclear test to mark the 1948 establishment of the Democratic People's Republic of Korea.
North Korea conducted its fifth nuclear test on September 9 last year, and then carried out a sixth a week ago, saying it was a hydrogen bomb that could be fitted on to a missile — prompting global condemnation and calls for further sanctions. In July, it tested two intercontinental ballistic missiles (ICBMs) that appeared to bring much of the mainland US into range.
The United States on Friday presented a draft resolution to the UN Security Council that calls for an oil embargo on North Korea, an assets freeze on leader Kim Jong-un, a ban on textile exports and an end to the hiring of North Korean guest workers. It is seeking a vote on the measures on Monday.
Diplomatic sources said Russia and China, which are pushing for a reopening of talks with North Korea instead, opposed all the measures except for the ban on textiles during a meeting of experts on Friday.
However, the US is willing to risk a veto of its proposal rather than see it watered down, according to a Security Council diplomat.
The Trump administration is also pressing individual governments to scale back diplomatic and economic ties with North Korea. Secretary of state Rex Tillerson raised the issue of North Korean “guest workers” in Kuwait during a meeting with the country’s foreign minister in Washington on Friday.
Faced with increasing pressure from the West, North Korea hit back at French leaders for suggesting that its nuclear ambitions posed a threat to Europe.
"It is ridiculous to say that the nuclear weapons of the DPRK, the deterrent force against the nuclear threat and blackmail of the US, can aim at Europe", said Ri Tok-son, deputy director of the North Korean foreign ministry's European department.
"If nuclear weapons are such bad things, then France should first give up its nuclear weapons since it is not under anyone's nuclear threat."
North Korea's state-run newspaper Rodong Sinmun said in an editorial on Saturday that Pyongyang was now a nuclear power and praised Mr Kim for his "brilliant achievement" in strengthening "defences to protect the Korean peninsula from invasion".
"The defence sector, in step with the party's Byungjin policy [of developing the economy and nuclear weapons at the same time] must make cutting-edge Juche weapons in greater quantities," the paper said, referring to the national philosophy of "Juche" or self-reliance.
The mouthpiece of the North's ruling party called for more "miracle-like events" such as the two ICBM tests to deter the United States which it said was bent on "decapitating" the nation's leader.
"No matter how the US and its puppets kick up a ruckus, our republic, which has a strong military and the most powerful Juche bombs and weapons, and whose territory has all turned into fortresses, and all its people armed to the teeth, will remain an eternal ironclad citadel," it said.
In another commentary, Rodong Sinmun said the US would continue receiving "gift packages in different shapes and sizes" as long as it sticks to what it said was a hostile policy against the North.
Mr Kim has called the ICBM tests "gift packages" that the North was delivering to the US.
A South Korean defence ministry spokesman said there were no signs of the North preparing a missile launch or a nuclear test on Saturday.
"The military is maintaining its utmost defence posture, keeping a close watch over the North. But there is nothing out of the ordinary," he said.
But he warned the North could fire ballistic missiles at any time from easily concealed mobile launchers.
South Korea's Yonhap news agency quoted a government official as saying that the North could carry out a seventh nuclear test at its Punggye-ri test site at any moment.
The official also said the North could choose the founding anniversary of the ruling Workers' Party, which falls on October 10, to hold another test.
Meanwhile, two Japanese fighters and two US bombers carried out a joint exercise over the East China Sea on Saturday, defence minister Itsunori Onodera said.
"It is important for us to display strong Japan-US relations for Japan's security," Mr Onodera said.