MARJAH, Afghanistan – U.S. Marines and Afghan soldiers advanced through poppy fields of Marjah on Saturday under withering gunfire from Taliban fighters shooting from mudbrick homes and compounds where families huddled in terror.

President Hamid Karzai urged NATO to do more to protect civilians during combat operations to secure Marjah, a southern Taliban stronghold and scene of the biggest allied ground assault of the eight-year war.

NATO forces have repeatedly said they want to prevent civilian casualties but acknowledged that it is not always possible. On Saturday, the alliance said its troops killed another civilian in the Marjah area, bringing the civilian death toll from the operation to at least 16.

Addressing the opening session of the Afghan parliament in Kabul, Karzai held up a picture of an 8-year-old girl who lost 12 relatives in a NATO rocket attack during the second day of the Marjah assault, which began Feb. 13.

Karzai said NATO had made progress in reducing civilian casualties and thanked the top commander, Gen. Stanley McChrystal, for ”standing with us honestly in this effort.” But Karzai said more needed to be done to protect civilians.

”We need to reach the point where there are no civilian casualties,” Karzai said. ”Our effort and our criticism will continue until we reach that goal.”

The Marjah operation is a major test of a new NATO strategy that stresses protecting civilians over routing insurgents as quickly as possible. It’s also the first major ground operation since President Obama ordered 30,000 reinforcements to Afghanistan.

Once the town is secure, NATO plans to rush in a civilian Afghan administration, restore public services and pour in aid to try to win the loyalty of the population and stop the Taliban’s return.

As the assault entered its second week, Marines and Afghan soldiers faced hours of sporadic but intense gunfights from insurgent snipers — often firing from compounds where families could be seen taking shelter. Troops crouched for cover in muddy ditches, firing rifles, machine guns and grenades as Taliban bullets whizzed by.

”We’ve been hurling lead all day,” said Lt. Carl Quist, who commands a platoon in the 3rd Battalion, 6th Marine Regiment.

U.S.-led troops have been pushing south from the town center against a pocket of Taliban fighters.

”They are running out of space now, that’s why they gotta fight and stand their ground,” Sgt. Melvin Adair, 28, of Clinton, Md., said of the Taliban.

A NATO statement said fighting was raging in the northeast and west of the town ”but insurgent activity is not limited to those areas.”

Twelve NATO troops have died in the offensive, and senior Marine officers say more than 120 insurgents have died. NATO reported Saturday that one of its service members was killed Friday in eastern Afghanistan.