“The international community, the UN Security Council and especially the other six-party powers must hold North Korea accountable for this latest act and heighten the pressure on North Korea especially through tightening of sanctions commensurate with the gravity of this act,” he said.

Carter, in particular, stressed the importance of China’s role.

“China shares important responsibility for this development and has an important responsibility to reverse it,” he said. “It’s important that it use its location, its history and its influence to further the denuclearization of the Korean peninsula and not the direction things have been going.”

The North detonated a nuclear device at its Punggye-ri underground nuclear test site on the country’s founding anniversary earlier Friday, just eight months after its fourth test in January, the first time the regime has conducted more than one nuclear test in a year.

Moreover, the latest test is believed to be the most powerful of all five, with its yield estimated at 10 kilotons of TNT, compared with January’s 6 kilotons, according to South Korea’s military. The powerful yield demonstrates the regime’s nuclear program is making real headway.

The previous four tests came in 2006, 2009, 2013 and January this year.

Secretary of State John Kerry vowed take “robust steps” against the North.

“The United States intends to work with UN Security Council partners to take robust steps in response to this provocation. We expect our Six Party Partners to take necessary steps to ensure the DPRK regime understands there are consequences to its unlawful and dangerous actions,” Kerry said in a statement.

The US remains open to “credible and authentic” denuclearization talks with the North, but Pyongyang “has chosen a different path and made clear it would not be a credible negotiating partner,” he said.

“North Korea will only achieve the security and development it claims to seek by living up to its international obligations and commitments,” he said. (Yonhap)