KABUL – The Afghan human rights commission reported Wednesday that 28 civilians have been killed so far in NATO’s offensive on the Taliban stronghold of Marjah, and urged pro-government forces to take greater care in distinguishing between noncombatants and militants.

The report came as Marines started a push to clear the last pockets of insurgents from Marjah in Helmand province. The 12th day of the offensive was relatively calm as the troops secured areas they’ve already taken and moved into position to tackle these final holdouts.

The Marjah assault is the largest military operation in Afghanistan since the ouster of the Taliban regime in 2001. Planners see it as key to taking on the insurgents in their southern heartland and turning around the war.

NATO has stressed the importance of protecting civilians as part of their counterinsurgency campaign, boosted by extra U.S. forces sent by the Obama administration.

But military officials say that despite the care taken, the offensive has still been marred by civilian deaths, including a rocket attack last week that hit a house and killed 12 people.

The Afghanistan Independent Human Rights Commission said in a statement Wednesday that it had confirmed 28 civilians deaths in the Marjah fighting, based on witness reports. Thirteen children were among the dead. About 70 civilians have been wounded, 30 of them children, the commission said.

NATO has confirmed at least 16 civilian deaths, while outside observers have reported 19.

Thirteen NATO service members and two Afghan soldiers have been killed in the operation. Eighty NATO troops have been wounded, along with eight Afghans, said a NATO official.

The Afghan commission said witnesses had told them that most of the civilian casualties came from coalition gunfire and rockets. Taliban fighters have been seen using women and children as human shields in the fighting — stationing them in windows or on roofs of houses from which they fire, according to military commanders and Associated Press reporters on the ground.

”We do appreciate the fact that less airpower was used,” commission spokesman Nader Nadery said. ”Still, as the operation continues and the number rises, we get more and more concerned.”

The commission asked for allied troops to exert greater care in distinguishing civilians from militants. Specifically, NATO forces should ”make sure that more of an assessment is carried out, and to as much as possible, avoid using rockets,” Nadery said.

The report also comes after a NATO airstrike Sunday in Uruzgan province killed at least 21 civilians, according to Afghan officials. NATO commander Gen. Stanley McChrystal apologized to the Afghan people for the deaths on national television.

The military alliance reported Wednesday that fighting was tapering off in Marjah, but bombs and gunmen continued to pose a threat.

Nevertheless, some residents have started to return, and NATO said a market in the north of Nad Ali district — of which Marjah is part — has opened for the first time in 18 months.

In the north of Marjah, more than 100 Marines and their Afghan counterparts pushed into a neighborhood they say is the last significant pocket of insurgents in the town.

About 100 fighters are believed to have regrouped in the 28-square-mile area known as Kareze, according to commanders with the 3rd Battalion, 6th Marines Regiment.

”The reports are that it’s where a lot of the bad guys went,” said Capt. Joshua Winfrey, head of Lima Company.

The United Nations on Wednesday called on all sides to do their utmost to protect children from the conflict.