The Democratic People's Republic of Korea (DPRK) on Friday accused the United States and South Korea of launching cyber attacks against it.

"Intensive and persistent virus attacks are being made every day on Internet servers operated by the DPRK," the official KCNA news agency said in a commentary.

The United States and South Korea "are massively bolstering up cyber forces in a bid to intensify subversive activities and sabotages against the DPRK," it added.

Internet access for both PCs and mobile phones in Pyongyang became unavailable on Wednesday morning due to hackers' attacks, according to the Star Joint Venture, a company that offers Internet services in the DPRK. The services were resumed Friday morning.

The DPRK's accusation came after Washington and Seoul began their "Key Resolve" joint military exercises on Monday despite Pyongyang's warning of annulment of the armistice agreement that halted the 1950-53 Korean War.

Tensions have been running high on the Korean Peninsula since the DPRK conducted its third nuclear test on Feb. 12.