The existence of the bases - which presumably would have to be declared and then dismantled under the US goal of North Korean "denuclearisation" - suggests that North Korea's previous efforts to dismantle known missile launch sites or nuclear facilities had little impact on its nuclear programme.
The report comes as talks between the US and North Korea hit another snag last week, with a New York meeting between Secretary of State Michael Pompeo and the top negotiator from Pyongyang cancelled at the last minute.
US President Donald Trump - who's cited North Korea's year-long freeze on nuclear weapons tests and ballistic missile launches as signs of progress - chalked up the change to a scheduling conflict, adding, "We think it's going fine, we're in no rush."
Yet pressure is building to ease international sanctions put in place last year, a move the Trump Administration is struggling to resist.
Last week, Russia called a meeting of the United Nations Security Council to take up its request for humanitarian exemptions to international sanctions on Pyongyang. The US said it would vet Russia's list, but Administration officials have previously said Moscow is already violating the restrictions.
The facilities identified in the new report are located in strategic locations that would put missiles in range of South Korea and Japan, according to the report. Some are likely to house missiles that could reach the continental US when they become deployed. For decades, the bases have been camouflaged to prevent destruction from pre-emptive strikes and during military operations.
The report singled out a base known as Sakkanmol, about 80km north of the demilitarised zone and one of the closest to South Korea.
The base, located in mountainous terrain, contains a unit equipped with short-range ballistic missiles, the report said, and could house medium-range ones. As of this month, "the base is active and being reasonably well-maintained by North Korean standards" with minor infrastructure changes.
- Bloomberg