Seoul's Foreign Ministry called the sanctions an "appropriate response," reiterating that cyberattacks to damage private and corporate interests and the openness and security of cyberspace should not be tolerated.
Those sanctioned will be banned from accessing the US financial system and doing any transactions with US nationals. But the largely symbolic sanctions are unlikely to further damage the economy of the heavily isolated country which is already under a series of international sanctions for its nuclear and missile tests.
The sanctions target the North's Reconnaissance General Bureau, the country's premier military spy agency, which Washington and Seoul believe orchestrated a series of cyberincursions against them. Seoul also blames the RGB for launching a string of fatal provocations including the 2010 torpedo attack on the corvette Cheonan that killed 46 sailors.
Korea Mining Development Trading Corp., in charge of the arms exports, and Korea Tangun Trading Corp., a defence research agency, have also been added to the sanctions list, as well as 10 senior officials, including those operating in Iran, Syria, China, Russia and Namibia.
"Even as the FBI continues its investigation into the cyberattack against Sony Pictures Entertainment, these steps underscore that we will employ a broad set of tools to defend US businesses and citizens, and to respond to attempts to undermine our values or threaten the national security of the United States," US Treasury secretary Jack Lew said in a statement.
The sanctions came as Pyongyang has hardened its rhetoric against the US, while continuing its peace offensive toward the South and refraining from launching its usual verbal attacks against Seoul.
"The US is wholly responsible for its hitherto antagonistic, hostile relationship with North Korea. The US should throw away its hostile policy toward the North," said a piece in Saturday's edition of the Rodong Sinmun, the daily of the North's ruling Workers' Party.
"Should the US come forward with good will while respecting our sovereignty without intervening in our internal affairs, we would respond to that accordingly."
The two Koreas have moved closer to dialogue since the North Korean leader demonstrated his desire to hold a "top-level meeting" with the South and restore cross-border ties in his New Year address.
Supporting the US sanctions against the North, Seoul appears to have reaffirmed that it would deal separately with the issues of inter-Korean cooperation and provocations such as the nuclear development and cybervandalism.
In response to Kim's New Year's address, Seoul reiterated that it remained open to dialogue in any form. Some observers said the North could specify its desire for inter-Korean talks this week, while others presume that it may wait until after President Park Geun-hye delivers her New Year's speech, which is expected to be delivered on Jan. 12.
The upcoming impediment to inter-Korean dialogue would be the planned annual military exercise between the US and South Korea, which will begin in February. The North Korean leader has called on the allies to cancel the exercise, but the South said the "defence" drills will proceed as planned.