Marjah, Afghanistan ? Taliban fighters stepped up counterattacks against Marines and Afghan soldiers in the militant stronghold of Marjah, slowing the allied advance to a crawl despite Afghan government claims that the insurgents are broken and on the run.

Taliban fighters appeared to be slipping under cover of darkness into compounds already deemed free of weapons and explosives, then opening fire on the Marines from behind U.S. lines.

Two NATO servicemembers died Monday from bomb strikes in Helmand, but neither was part of the Marjah offensive, military spokesman Sgt. Kevin Bell said. NATO did not provide their nationalities.

Also on Monday, NATO said five civilians were accidentally killed and two wounded by an airstrike when they were mistakenly believed to have been planting roadside bombs in Kandahar province, east of the Marjah offensive.

The airstrike happened one day after 12 people, half of them children, were killed by two U.S. missiles that struck a house on the outskirts of Marjah. Afghan officials said Monday that three Taliban fighters were in the house at the time of the attack.

On the third day of the main attack on Marjah, Afghan commanders spoke optimistically Monday about progress in the town of about 80,000 people, the linchpin of the Taliban logistical and opium poppy smuggling network in the militant-influenced south.

Brig. Gen. Sher Mohammad Zazai, commander of Afghan troops in the south, told reporters in nearby Lashkar Gah that there had been “low resistance” in the town, adding “soon we will have Marjah cleared of enemies.”

Interior Minister Hanif Atmar said many insurgent fighters had already fled Marjah, possibly heading for Pakistan.

In Marjah, however, there was little sign the Taliban were broken. Instead, small, mobile teams of insurgents repeatedly attacked U.S. and Afghan troops with rocket, rifle and rocket-propelled grenade fire. Insurgents moved close enough to the main road to fire repeatedly at columns of mine-clearing vehicles.

At midday at least six large gunbattles were raging across the town, and helicopter gunships couldn’t cover all the different fighting locations.

Allied officials have reported only two coalition deaths so far — one American and one Briton killed Saturday. There have been no reports of wounded. Afghan officials said at least 27 insurgents have been killed so far in the offensive.

Nonetheless, the harassment tactics and the huge number of roadside bombs, mines and booby traps planted throughout Marjah have succeeded in slowing the movement of allied forces through the town. After daylong skirmishes, some Marine units had barely advanced at all by sundown.

As long as the town remains unstable, NATO officials cannot move to the second phase — restoring Afghan government control and rushing in aid and public services to win over inhabitants who have been living under Taliban rule for years.

Afghan President Hamid Karzai approved the assault on Marjah only after instructing NATO and Afghan commanders to be careful about harming civilians. “This operation has been done with that in mind,” the top NATO commander, U.S. Gen. Stanley McChrystal, said Monday.

Despite those instructions, NATO said two U.S. rockets veered off target by up to 600 yards and slammed into a home Sunday outside Marjah, killing 12 people. Six children were among the dead, a NATO military official confirmed Monday, speaking on condition of anonymity because the information had not been formally released.