Marjah , Afghanistan ( CNN ) -- U.S. Marines fighting the Taliban in southern Afghanistan achieved a main objective Tuesday -- taking over the police headquarters in the center of the Taliban stronghold of Marjah . CNN correspondent Atia Abawi , embedded with the Marines , said troops did n't receive any resistance when they took the station , but gun battles broke out in the area a few hours later . There was an engagement for 15 to 20 minutes , with constant gunfire coming from different directions , and there have been `` sporadic battles , '' Abawi said . Unlike previous days , there was fighting in the evening , with Taliban militants trying to attack Marine locations with small arms and rocket-propelled grenades . One of the grenades hit close to one of the U.S. positions and a fire broke out . About 15,000 Afghan and NATO forces are taking part in Operation Moshtarak , which focuses on the town of Marjah and surrounding areas in Helmand province . Set in a region known as the country 's heroin capital , Marjah is where the Taliban established a shadow government . The military says the goal of Operation Moshtarak is to provide security , governance and development , and authorities hope fighters choose to reject the insurgency and join the government 's reintegration process . Clearing out poppy fields is a key part of the push , the biggest since the Afghanistan War started in 2001 . The Taliban finances its activities in part through the illegal opium trade . One of the biggest challenges facing the NATO mission in Afghanistan is attacking the Taliban while limiting civilian casualties . On Sunday , 12 civilians died in a rocket attack by coalition troops . Three other Afghan civilians were killed by NATO in separate incidents on Sunday and Monday . On Tuesday , Abawi spoke to one civilian whose property had been destroyed in the initial push by Marines . Despite that , he said he was happy to see Americans arrive and noted that Marines promised to pay for the damages to his home . He said Afghans have suffered under the Taliban , who he said had beheaded some people and forced their way into people 's homes for food .
Operation Moshtarak focuses on area where heroin produced , Taliban has shadow government . Taliban finances uses illegal opium trade to finance activities . Gun battles broke out hours later after headquarters seized , CNN correspondent says . Taliban militants try to attack Marine locations with small arms and rocket-propelled grenades .