Though there has been no comment from the authorities in Pyongyang, South Korean officials and US experts reported the restoration.
Some analysts say the country's web access was cut entirely for a time.
China meanwhile has denounced reports suggesting it was responsible for the North Korean online shutdown.
Foreign Ministry spokeswoman Hua Chunying said that such reports were "speculative" and had "no basis in reality".
"These reports themselves are extremely irresponsible, unprofessional and misleading," she added.
China's permanent representative to the United Nations has called for all sides to avoid an escalation of tension on the Korean Peninsula after the UN Security Council put the North's human rights record on its agenda.