South Korean Foreign Minister Yun Byung-Se on Wednesday urged the UN Security Council to threaten North Korea with "the most serious consequences" if it refuses to stop conducting nuclear tests.

North Korea has recently been testing the engine for an inter-continental ballistic missile amid concerns it is preparing a fourth nuclear test, with recent satellite images showing increased activity at its main nuclear test site.

"We must clearly warn North Korea that if it challenges the international community with another nuclear test it will be met with the most serious consequences," the minister said.

Pyongyang has already conducted nuclear tests in October 2006, May 2009, and February 2013, despite bans by the United Nations and increased international sanctions.

"Further nuclear tests by North Korea must be prevented through concerted efforts of the international community," Yun added.

"If we fail to effectively act upon such a clear and present threat to international peace and security, it would critically weaken the credibility of the Security Council as well as the integrity of the UN charter."

North Korea's UN representative Ri Tong-Il accused the United States of being "the mastermind of the proliferation of nuclear weapons" and justified North Korea's tests as "self-defensive."

Washington, Ri added, had helped Israel acquire nuclear weapons but had only "increased nuclear blackmail" against North Korea.

The North Korean ambassador was cut short by South Korea -- which has taken over the rotating presidency of the Security Council for May -- for exceeding his allotted time limit.

The Security Council was debating non-proliferation on the 10th anniversary of resolution 1540. South Korea leads the committee for enforcing the resolution.

The council's members unanimously approved a declaration recalling the objectives of resolution 1540, which first passed in 2004.

The declaration notably asks states to take national measures to ensure weapons of mass destruction do not end up in the hands of terrorists.