The sanctions on North Korea target what is increasingly being seen as a key means of financing the country's nuclear build-up -- coal exports.
The United Nations is imposing a new binding cap on how much coal can be shipped out of the country.
South Korea's ambassador to the United Nations, Oh Joon, estimates more than $1.3 billion has already been spent on testing and missile-launching.
"This could have been used to buy one year's worth of food for the entire North Korean population. People need to eat food, not weapons. For reasons defying any common sense, Pyongyang is paying a heavy price to gain a nuclear arsenal at the expense of its own people. If they had used those resources for people's livelihoods, the North Korean population's hardship would have been much relieved."
The South Korean ambassador has also spoken passionately about his own country's feelings towards its northern neighbour and the prospect of reunification.
"When we watch North Korean missile launches on television, we feel as if a brother in the family is wielding a gun, shooting in the air, while his children are screaming."
The 15-member Security Council unanimously agreed to the sanctions, which follow North Korea's fifth -- and largest -- nuclear test in September.
The resolution cuts coal exports by 60 per cent, with an annual cap of $540 million a year.
Copper, nickel, silver and zinc exports will also be restricted.
UN secretary-general Ban Ki-Moon says the sanctions are some of the toughest and most comprehensive ever imposed on North Korea, or the Democratic People's Republic of Korea.
"It sends an unequivocal message that the DPRK must cease further provocative actions and comply fully with its international obligations. Targeted sanctions matter. The Security Council sanctions represent the clear and unified will of the international community."
The United States' UN ambassador, Samantha Power, is urging North Korea to negotiate with the international community on complete, verifiable denuclearisation.
"The United States is realistic about what this resolution will achieve. No resolution in New York will likely, tomorrow, persuade Pyongyang to cease its relentless pursuit of nuclear weapons. But this resolution imposes unprecedented costs on the DPRK regime for defying this council's demands. The DPRK is determined to refine its nuclear- and ballistic-missile technology to pose an even more potent threat to UN member states and, more broadly, to international peace and security."
The sanctions will have a major impact on China, believed to be the only country buying North Korean coal.
This year alone, its imports have been up almost 13 per cent.
While opposed to North Korean nuclear testing, China has criticised South Korea and the United States for strengthening their military presence on the Korean Peninsula.
China's UN ambassador, Liu Jieyi, has told the council the planned US high-altitude anti-missile system would undermine China's security interests and upset the regional balance.
"As such, it is neither conducive to the realisation of the goal of denuclearisation of the Korean Peninsula nor helpful for the maintenance of peace and stability on the peninsula."
Russia's UN representative, Vladimir Safrankov, has expressed his country's reservations about the impact of sanctions on the North Korean population.
"We stress, in particular, this new resolution can in no way be used to smother the North Korean economy and worsen the humanitarian situation and the situation of the people living in that country."
He has also warned against using the situation on the Korean Peninsula as a pretext for enhancing foreign military capacities.
