Seoul prosecutors on Monday accused North Korea of hacking into the email accounts of dozens of South Korean government officials this year, the latest in the series of suspected cyber attacks by Pyongyang.

Investigations showed a "suspected North Korea-operated group" attempted to hack into the emails of 90 people -- including officials at the foreign, defence and unification ministries -- from January to June, the Supreme Prosecutors' Office said in a statement.

"The passwords of 56 accounts were stolen," the statement said.

The hackers set up 27 phishing sites in January posing as popular portals like Google and South Korea's Naver, as well as government and university websites, to steal the passwords.

The prosecutors said the malicious codes used in the latest attack were the same as the ones used by North Korea in previous attacks on the South.

An investigation is still ongoing to see if any confidential information may have been leaked.

The latest cyber attack comes just days after South Korean police said the North stole the personal data of over 10 million customers at South Korean online shopping mall Interpark.

Interpark was unaware about the attack until July 11, when it was blackmailed with threats to publicise the leaked data unless the company paid three billion won (US$2.7 million).

The National Police Agency said the North's main spy agency -- the Reconnaissance General Bureau -- had organised the hack in a bid to earn hard currency.

Tensions on the divided Korean peninsula have been running high since Pyongyang carried out its fourth nuclear test in January, followed by a series of ballistic missile tests.

The provocations have put North Korea under the toughest sanctions yet from the United Nations as well as mounting individual sanctions by countries like the US, South Korea and Japan.

Seoul has in recent years blamed the North's hackers for a series of cyber attacks on military institutions, banks, state agencies, TV broadcasters, media websites and a nuclear power plant.

The North operates an army of more than 1,000 hackers who stage hacking or cyber attacks targeting Seoul's major institutions or key officials, according to the South's spy agency.