The National Unity Government (NUG), which claims to be the country's legitimate government, was formed last April and is made up of dissident lawmakers in hiding or exile, many of them from ousted leader Aung San Suu Kyi's party.
Several months earlier, on February 1, the junta had grabbed power by alleging massive fraud during elections in late 2020 which Suu Kyi's National League for Democracy won by a landslide.
Suu Kyi, who won the 1991 Nobel Peace Prize, has been under house arrest at a secret location since the coup, ending a brief democratic interlude for the country.
The coup has plunged the country into chaos.
More than 1,500 civilians have been killed by security forces, according to a local aid organisation, and "people's defence forces" have taken up arms against the military across the country.
Activists on Tuesday called for silent strikes to mark the first anniversary of the coup.
The NUG has a "democratic legitimacy", Elvestuen said.
"It is keeping democratic institutions and principles afloat", he added.
The deadline for Nobel Peace Prize nominations was 31 January. This year's winner will be announced in early October.
Among the other nominations already known to have been submitted are Myanmar's civil disobedience movement, Swedish climate activist Greta Thunberg, British naturalist David Attenborough, Pope Francis and Belarusian opposition leader Svetlana Tikhanovskaya.
Thousands of people are eligible to submit nominations for the Nobel Peace Prize, including lawmakers and cabinet members of all countries, former laureates and some university professors.