New video from an apartment complex in Aurora shows six men wandering the halls, climbing a staircase and banging on a unit's front door ... and five of the men are packing heat.

One of the men is openly carrying what appears to be an assault rifle -- check out the huge scope on the gun -- while the other four are walking around with handguns.

There have been lots of reports of issues recently with a Venezuelan gang, Tren de Aragua, in Denver and now Aurora ... once a quiet suburb.

Aurora city council member Dani Jurinsky claims a gang has taken over several apartment complexes in town.

The video is going viral on social media, and it seems to have popped up on the Denver Police Department's radar ... because cops put out a statement Wednesday saying the force "takes the presence of Tren de Aragua seriously."

Denver PD says there are reasons to believe gang members are tied to crimes in the area, but they say they are not aware of any apartment buildings being "taken over" by this gang in Denver ... though the video technically is out of Aurora.