A powerful underground nuclear test conducted by North Korea on Monday requires a determined international reaction "in order to send a message to other countries," a Foreign Ministry statement from Jerusalem said Monday. The Foreign Ministry viewed with "extreme gravity" North Korea's second nuclear test, and said Israel was a partner to the international concern over North Korea's action. Likewise, the statement said, "Israel is concerned about North Korea's proliferation, which has negative ramifications for our region." US President Barack Obama assailed North Korea for the missile tests, saying the world must "stand up to" Pyongyang and demand that it honor a promise to abandon its nuclear ambitions. Monday's test - much larger than one North Korea conducted in 2006 - is considered a major provocation in the escalating international standoff over its rogue nuclear and missile programs. The regime "successfully conducted one more underground nuclear test on May 25 as part of measures to bolster its nuclear deterrent for self-defense," the country's official Korean Central News Agency said. Russia's Defense Ministry confirmed an atomic explosion at 9:54 a.m. local time in northeastern North Korea, estimating the blast's yield at 10 to 20 kilotons - comparable to the bombs that flattened Hiroshima and Nagasaki. Hours later, the regime test-fired three short-range, ground-to-air missiles, the Yonhap news agency reported, citing unnamed sources. UN Security Council resolutions bar North Korea from engaging in any ballistic missile-related activity. Appearing on the White House steps, Obama said that North Korea's underground test and subsequent test firings of short-range ground to air missiles "pose a grave threat to the peace and security of the world and I strongly condemn their reckless action." It was his second statement within hours on the tests, the latest in a number of nuclear actions that Obama said "endanger the people of Northeast Asia." He called it "a blatant violation of international law" and said that it contradicted North Korea's "own prior commitments." Obama had released a written statement chastising the North Koreans in the early Monday morning. In his statement before cameras and microphones arrayed in the White House Rose Garden at mid-morning, he noted that the latest tests had also been denounced by China and Russia and had drawn the scorn of many around the world. Pyongyang's actions "have flown in the face of UN resolutions" and had deepened its isolation, he said, "inviting stronger international pressure. "By acting in blatant defiance of the United Nations Security Council," he said, "North Korea is directly and recklessly challenging the international community. North Korea's behavior increases tensions and undermines stability in Northeast Asia. "North Korea will not find security and respect through threats and illegal weapons," the president said. "We will work with our friends and allies to stand up to this behavior. The United States will never waver from our determination to protect our people and the peace and security of the world." UN Secretary-General Ban Ki-moon said that if North Korea's claim can be confirmed, its announcement of a second nuclear test would represent "a clear violation" of a United Nations Security Council resolution. "I sincerely hope that the Security Council will take necessary corresponding measures," Ban told The Associated Press, declining to specify what further moves, or sanctions, he would urge the 15 council members to take. The council scheduled emergency consultations on North Korea's actions for Monday afternoon, late Monday night Israel time. British Prime Minister Gordon Brown condemned the test as "erroneous, misguided and a danger to the world." "North Korea's nuclear test poses a grave challenge to nuclear nonproliferation and clearly violates UN Security Council resolutions," Japanese Prime Minister Taro Aso said in Tokyo. "We are not tolerating this at all." Even China, North Korea's traditional ally, issued rare criticism of Pyongyang, with the Chinese Foreign Ministry saying in a statement posted on its Web site that Beijing was "resolutely opposed" to the test. Russia's Foreign Ministry called the test "a serious blow to international efforts" to prevent the spread of nuclear weapons. Reining in Pyongyang's nuclear program has been a continuing problem for US administrations, dating to Bill Clinton's presidency in the 1990s. Former President George W. Bush labeled North Korea as a country that was part of an international "axis of evil," but the United States subsequently removed Pyongyang from its list of official state sponsors of terrorism when it shut down a nuclear installation late in the Bush administration. The question now is calculating precisely the nature of a threat and what are options are available to the Obama administration. "We are gravely concerned by North Korea's claims. We are analyzing the data," the State Department said in a statement. "The US Geological Survey confirmed that a seismic event took place consistent with a test. We are consulting with our Six Party and UN Security Council partners on next steps." The six parties that had participated in discussions after North Korea withdrew from the international Nuclear Nonproliferation Treaty in 2003 were China, the US, Japan, Russia and South Korea and North Korea itself. North Korea abandoned the talks last month over the UN condemnation of an April 5 rocket launch. North Korea claims it launched the rocket to send a satellite into space; South Korea, Japan and other nations saw it as a way to test the technology used to launch an intercontinental ballistic missile. Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, last month dismissed the earlier rocket launch as a failure - both technologically and as an effort to market its missiles to other countries. "Would you buy from somebody that had failed three times in a row and never been successful?" he asked during a briefing at the Pentagon. Cartwright said the abortive missile launch showed that North Korea had failed to master the midair thrust shift from one rocket booster to another, an integral part of ballistic missile technology. Adm. Mike Mullen, chairman of the US Joint Chiefs of Staff, said he believed the latest series of tests "just speak to the growing belligerence on the part of North Korea ... the growing defiance of international law." Mullen, appearing on CBS television, said that "all of those things point to a country I think continues to destabilize that region and in the long term, should they continue to develop a nuclear weapons program, poses a grave threat to the United States." Mullen, making appearances on various TV morning news shows Monday to pay tribute to troops on America's Memorial Day, told NBC that he was "very confident we can deal with a threat posed by North Korea." "It's not just the US, but there are many other countries that are equally concerned," the admiral said. "This was not an unanticipated test on the part of North Korea, should we be able to confirm it. ... It's a country that continues to isolate itself, and the international community must continue to bring pressure to make sure they don't achieve a nuclear weapons program that can threaten other countries and the US as well." He did not say whether there were any changes in US military alert status.