The activation of the new line from TransTeleCom was first detected Sunday by analysts at Dyn Research, which monitors global internet connectivity.
The new connection supplements the existing link provided by China Unicom, which has almost exclusively routed North Korean internet traffic since 2010.
The additional line gives Pyongyang "significantly more resilience against attacks on their network infrastructure," said Bryce Boland, the chief technology officer in the Asia- Pacific for cybersecurity firm FireEye.
The operation ended Saturday, the report said.
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North Korea has a 6,800-strong unit of trained cyberwarfare specialists, according to Seoul's defence ministry, and has been accused of launching high-profile cyberattacks including the 2014 hacking of Sony Pictures.
But with only one internet provider to rely on, the regime has often found itself vulnerable to external cyberattacks against its own network infrastructure.
North Korea suffered several internet connection failures -- some which lasted for hours -- shortly after the Sony attack, which many suspected to be a US retaliation.
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