Abu Sayyaf released Kjartan Sekkingstad at 4 p.m. local time (4 a.m. ET), according to Western Mindanao Command spokesman Maj. Filemon Tan Jr.
Sekkingstad's release was an offshoot of ongoing military operations against the Abu Sayyaf group, Tan told CNN Philippines. The Moro National Liberation Front, which is in peace talks with the government, assisted authorities in the operation, he said.
"Simultaneous land, air, naval and police operations complemented each other putting pressure on (Abu Sayyaf)," Tan said.
It is unclear whether a ransom was paid to secure Sekkingstad's release.
Speaking at a press conference on Sunday, Philippines President Rodrigo Duterte said "it was a long, long negotiation."
At the same conference, Sekkingstad expressed his "heartfelt" gratitude to the President, adding that he was "happy to be alive and free and it is a beautiful feeling."
Abducted from resort
Sekkingstad was abducted from a resort on Samal Island, which lies off the coast of the major southern island of Mindanao, on September 21, 2015.
Three people were kidnapped with him: Canadians John Ridsdel and Robert Hall, and Filipina Tess Flor. Hall, Ridsdel and Flor were visiting the resort's marina on their yacht and Sekkingstad was the manager of the property.
Abu Sayyaf initially demanded a $6.3 million ransom for each of the victims to be paid by April 25, according to Philippine state media.
In April, after murdering Canadian hostage Ridsdel, the group reset the deadline to June 13 for the remaining three hostages.
A video obtained in May by SITE, a group that monitors extremist and terrorist groups, showed three hostages sur