A logo is pictured outside Sony Pictures Studios in Culver City, California December 19, 2014. [Photo/Agencies]

HONOLULU - The US imposed new sanctions on the Democratic People's Republic of Korea (DPRK) on Friday, targeting top state officials and defense-related organizations in an attempt at punishment for a crippling cyberattack against Sony. The sanctions marked the first public act of retribution by the US.

Although it was unclear how punishing the blow would be, as DPRK already is under tough US sanctions for its nuclear program, the announcement signaled that the US was not backing away from its insistence that DPRK is responsible for the attack against Sony. DPRK has denied involvement, and some cybersecurity experts say it's possible Pyongyang wasn't to blame.

"The order is not targeted at the people of DPRK, but rather is aimed at the government of DPRK and its activities that threaten the US and others," US President Barack Obama wrote to a letter to House of Representatives and Senate leaders.

None of the 10 individuals targeted by the US are being sanctioned because they had any involvement in the cyberattack, Obama administration officials said. Rather, the US sanctions were aimed at undermining DPRK's defense sector, further isolating the government and creating a deterrent for future cyberattacks, said the officials, who briefed reporters on condition of anonymity.

The White House warned this was just the first part of the US response to the Sony incident. Officials said more individuals will be sanctioned in the future.

The new sanctions, authorized by Obama, also will affect three DPRK entities that are already subject to some US sanctions. The 10 individuals work for those entities or the DPRK government. These are the first US sanctions punishing Pyongyang for alleged cyberattacks.

The FBI has blamed DPRK for the cyberattack against Sony Pictures Entertainment. DPRK has denied involvement but has expressed fury over a comedy film by Sony that mocked leader Kim Jong-un. Sony Pictures initially called off release of the film, citing threats of terror attacks against US movie theaters. Obama criticized Sony's decision, and the movie opened last month.

A nearly 10-hour shutdown of DPRK websites last week prompted widespread speculation that the US had launched a counterattack in retribution, but the White House did not comment on whether the US was responsible. The US has vowed a proportional response to the Sony incident but has warned its response would "take place at a time and in a manner of our choosing."

DPRK and the US are already in an international standoff over DPRK's nuclear and missile programs and its alleged human rights abuses.

Among those sanctioned Friday are organizations tied closely to DPRK's defense industry:

- Korea Mining Development Trading Corporation, the state-owned arms dealer and exporter of equipment related to ballistic missiles and conventional weapons.

- Korea Tangun Trading Corporation, which obtains technology to support DPRK's defense research.

- Reconnaissance General Bureau, DPRK's primary intelligence organization that runs the country's cyber warfare.

Obama signed an executive order authorizing the sanctions from Hawaii, where he is on vacation with his family.