North Korea brought down a cooling tower at its nuclear plant today according to reports from South Korean broadcaster MBC, which has a crew at the site.
The move was part of a process of dismantling the state's nuclear programme in return for easing its international isolation.
Pyongyang yesterday handed over an account of its nuclear programme, fulfilling a key requirement in six-nation talks on halting North Korea's nuclear weapons programme and creating a nuclear-free zone on the Korean peninsula.
Global powers still need to verify the claims Pyongyang made in its atomic inventory and experts say the dramatic event will leave unresolved questions about the North's declaration, such as accounting for its nuclear weaponry.
But shortly after North Korea handed over the list yesterday, the United States responded by saying it would take the state it once branded as being part of "an axis of evil" off of its terrorism blacklist and ease some sanctions.
The secretive North had invited in five foreign media outlets to witness the destruction of the tower, which is connected to its Soviet-era reactor.
Steam coming from the tower in spy satellite photographs has been the most visible signs of operation at the facility, capable of producing arms-grade plutonium.
"The problem is that they always feel that they can continue to game the system and appear to keep the window open - actions like blowing up cooling towers on TV for propaganda effect that I'm not sure have much practical effect," said Derek Mitchell, Asia expert at the Center for Strategic and International Studies.
US President George W. Bush cautiously welcomed the declaration but warned North Korea, which tested a nuclear device in October 2006, that it faced "consequences" if it did not fully disclose its operations and continue to dismantle its nuclear programmes.
Responding to an unusual opening by the secretive communist state, Mr Bush took a step toward removing North Korea from a US list of state sponsors of terrorism and issued a proclamation lifting some sanctions under the Trading with the Enemy Act.
Once it is removed from the lists, North Korea will be able to better tap into international finance.
Due to the small size of North Korea's shaky economy, any increases in investment and trade could have major effects, experts said, but added increased revenue would likely make its way to Pyongyang's leaders and further solidify their rule.
US officials acknowledged that the North Korean declaration, which came six months after a December deadline, fell short of answering all concerns about Pyongyang's atomic ambitions, especially on past nuclear proliferation activities.
Stephen Hadley, Bush's national security adviser, said the statement revealed the amount of plutonium North Korea had produced but did not detail its nuclear arsenal.
But he said US experts could "do the math" and that issue would be discussed in a further phase of the so called six-party talks.
Under a deal North Korea struck with China, Japan, Russia, South Korea and the United States, Pyongyang was required to start taking apart its Yongbyon nuclear plant and provide the nuclear list by the end of 2007.
US and South Korean officials said North Korea has taken most of the steps to put the Yongbyon facility - that includes the reactor, a plant to make nuclear fuel and another to turn spent fuel into plutonium - out of business for at least a year.