North Korea on Sunday blasted Seoul's accusation that Pyongyang had launched a series of cyber attacks targeting South Korean government officials, calling the allegation a "bullshit" fabrication.

Seoul's National Intelligence Service (NIS) last week accused North Korean agents of hacking into the smartphones of dozens of key South Korean officials, stealing phone numbers and texts.

The accusation follow claims earlier this year from the NIS that North Korean hackers sent phishing emails to the South's state railway authorities in preparation for cyber terror attacks on traffic control systems.

The North's state-run Rodong Sinmun newspaper lashed out at the hacking accusations, saying they were cooked up by Seoul to shore up support for controversial surveillance legislation.

"This is such shameless bullshit from the enemy forces who are obsessed with confrontation and political slander," read an editorial published on Sunday.

It added that Seoul was trying to use the "fabricated" threats to rally support for an anti-cyber terror bill that would the grant the NIS greater surveillance powers on the Internet.

The controversial bill, which critics say could be used against political opponents, is pending in the National Assembly.

Seoul has blamed North Korean hackers in the past for a series of cyber-attacks on military institutions, banks, government bodies, TV broadcasters and media websites as well as a nuclear power plant.

The US also said the North was behind a crippling cyber-attack on Sony's Hollywood film unit over its controversial North Korea-themed satirical film "The Interview" in 2014.

Pyongyang has denied involvement in the attacks and accused South Korean of spreading fabrications aimed at slandering its leader.

Military tensions on the divided Korean peninsula have been on the rise since the North carried out its fourth nuclear test in January, followed by a long-range rocket launch last month.

On Saturday, the North pledged to launch a "blitzkrieg" in the Korean peninsula, as the United States and South Korea launched their largest-ever joint landing drill.