The decision followed a series of social media posts by Chief of Defence Forces General Muhoozi Kainerugaba announcing action against the media house.
According to the Daily Monitor, security personnel deployed shortly after midnight at the NMG premises in Namuwongo and at Kampala Serena Hotel, with staff reporting they were prevented from entering or leaving the premises as the operation unfolded.
The newspaper reported that NTV Uganda and Spark TV were forced off air by about 5am, with viewers encountering blank screens displaying the message "video unavailable."
Daily Monitor also reported that Dembe FM and KFM, who broadcast from their premises in Namuwongo, were taken off air during the operation.
The security deployment followed a string of posts on X by Gen Muhoozi in which he declared that NTV Uganda and the Daily Monitor would be shut down.
NMG-U had not released an official statement at the time of publishing this article.
The shutdown is the latest confrontation between the State and one of Uganda's largest independent media organisations.
In May 2013, police raided the Daily Monitor and Dembe FM - as well as Red Pepper in Namanve - following publication of a letter allegedly linking senior government officials to the so-called "Muhoozi Project."
Over the years, President Museveni has repeatedly criticised the Daily Monitor, at one point describing it as an "enemy and evil newspaper" over its editorial coverage.