SEOUL - Hackers say they have leaked personal details of tens of thousands of US troops to websites, South Korean news reports and online security officials said on Wednesday, a day after cyber attacks disabled access to government and news sites.

The hacking attacks on Tuesday, the anniversary of the start of the Korean War in 1950, brought down the main websites of South Korea's presidential office and some local newspapers, prompting cyber security officials to raise the alert.

The identity and motives of the attackers were not immediately clear, but the reports come as cyber security and surveillance have become a global issue, with the United States seeking fugitive former security contractor Edward Snowden who leaked details about US surveillance to the media.

North Korea has been blamed for previous cyber attacks on South Korean banks and government networks, although it denies responsibility and has said it has also been a victim.

The unidentified hackers said they had secured and released publicly personal details of more than two million South Korean ruling party workers and 40,000 US troops, including those stationed in South Korea.

"We have seen the sites where the details were posted and clips that supposedly capture the process of hacking into web sites," an official at the South Korean online security firm NSHC said.

The legitimacy of the information could not be verified, the official who requested anonymity said.

An official at the Communications Ministry said authorities were probing the nature of the attacks and declined to comment on the reports of leaked information about US troops.

The US military in South Korea, where 28,500 US troops are stationed, did not immediately comment.

North and South Korea remain technically at war after their 1950-53 conflict ended in a truce, not a peace treaty. The US troops' presence is aimed at ensuring the truce holds.

News reports said personal details such as dates of birth and ranks of 40,000 US troops including members of the 25th Infantry Division and the 3rd Marine Division were leaked to unspecified websites.

The websites of the presidential Blue House and the Prime Minister's office were down for more than six hours on Tuesday.

North Korea is believed to be running a large corps of computer experts aimed at hacking into the networks of governments and financial institutions and was blamed most notably for the 2011 shutdown of a South Korean commercial bank.

Last week it accused the United States of being at the forefront of rights abuse, pointing to Snowden's revelations of mass surveillance operations by the National Security Agency.

On Tuesday, access to some North Korean news sites was blocked after the hacker group Anonymous vowed to direct a denial-of-service attack direct at them.