The US military's Marines are conducting training exercises in downtown Los Angeles, the local CBS affiliate reports.

Residents in and around downtown Los Angeles could hear helicopters or other military aircraft over the coming days as Marines and sailors from Camp Pendleton train in preparation for a deployment.

The training is part of a two-week military exercise that starts Friday and extends through Dec. 16 and involves about 2,400 members of the 15th Marine Expeditionary Unit, according to the Associated Press.

While residents could see as many as six military helicopters buzzing over the downtown area over the next week, raids being held at several undisclosed locations in the city will be off limits to the public for safety reasons, Capt. Brian Block told the Associated Press.

Why are the Marines training in a domestic city?  “This is one location amongst many that the Marines are gonna be kind of exposing their people to," an LAPD commander told local journalists. Why must Marines be "exposed" to the terrain in downtown LA? Do the Marines intend to occupy Los Angeles?

The military has been training in cities across the United States in recent years, for unknown reasons. Similar exercises have taken place in St. Louis, Miami, Houston, and Boston, among others.

The police are becoming more militarized, and the military is training in US cities. What's going on here?