NATO troops clearing out Taliban stronghold, officials say

Operation Moshtarak, in the southern city of Marjah, is going "very smooth" so far, U.S. Marine Corps Lt. Col. Mark Dietz told CNN Monday.

He said the Marines had bypassed several lines of roadside bombs and were in the process of clearing the city "from the inside out."

There has been some active combat, said CNN's Atia Abawi, who is embedded with U.S. Marines in Marjah.

The Taliban is "popping up in various parts of the city," Abawi said. "We went just a couple hundred meters outside of the position that we're usually based in -- we were under gunfire ourselves."

Marjah is "practically a ghost town right now," she added. "You can't really find out where they're hiding. ... They can be anywhere."

Abawi said NATO forces are hoping to draw more "extremist fighters" out of their hiding places and into combat. Between two and three insurgents are being killed in each clash on average, she said, and NATO commanders "don't expect [fighting] to die down anytime soon."

Combined forces have been "conducting a number of mounted and dismounted patrols," according to a news release from the International Security Assistance Force.

"Elements of the combined force have been engaged in periodic small arms fire fights, and a number of insurgents have been either killed or detained," ISAF said.