North Korea has called increased UN sanctions a "hostile act", committed with the intention to "physically exterminate" its citizens.
In response to new sanctions - imposed after the country's sixth and most powerful nuclear test - the state has said it will now accelerate its nuclear programme.
A foreign ministry spokesman for the North called the sanctions "the most vicious, unethical and inhumane act of hostility", intended "to physically exterminate the people of the Democratic People's Republic of Korea (DPRK)".
Fresh measures - including banning textile imports and capping petrol supply - were unanimously imposed by the UN Security Council against Pyongyang one week ago.
The mandate came after North Korea successfully fired a Hwasong-12 intermediate-range ballistic missile over Japan at the beginning of September, in defiance of existing sanctions.
Pyongyang launched a second ballistic missile across Japan two weeks later.
As North Korea responded to the sanctions on Monday, US bombers and jets have been conducting "mock bombing drills" over the Korean peninsula, in what was described by South Korea's Yonhap news agency as a further show of force.
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A pair of B-1B bombers and four F-35 jets flew from Guam and Japan, joining four South Korean F-15K fighters as part of the latest drill.
China's foreign ministry spokesman has said that by sending "threatening messages" including "warnings of military action", the US is "further complicating the situation".
The People's Daily, China's Communist Party newspaper, has argued that the sanctions need longer to take effect and should not be used as "a tool for stifling the regime".
Russia and China have also begun naval exercises not far from the Russia-North Korea border, to the north of Japan.
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As the diplomatic situation continues to escalate, Germany's foreign minister has called for direct talks between the US, China and Russia.
However, Japanese Prime Minister Shinzo Abe has previously said diplomacy and dialogue will not work with Pyongyang, calling for the entire international community to apply more pressure.
The fear remains that Kim Jong Un may soon develop the ability to target the US with a powerful, nuclear-tipped missile.
A UN General Assembly meeting will be held on on Tuesday, with North Korea's nuclear threat expected to be high on the agenda.