US Marines have come under heavy fire in Marjah
Taliban militants are increasingly using civilians as "human shields" as they battle against a joint Afghan-Nato offensive, an Afghan general has said.
Gen Mohiudin Ghori said his soldiers had seen Taliban fighters placing women and children on the roofs of buildings and firing from behind them.
The joint offensive in southern Helmand province has entered its fifth day.
US Marines fighting to take the Taliban haven of Marjah have had to call in air support as they come under heavy fire.
They have faced sustained machine-gun fire from fighters hiding in bunkers and in buildings including homes and mosques.
Gen Ghori, the senior commander for Afghan troops in the area, accused the Taliban of taking civilians hostage in Marjah and putting them in the line of fire.
"Especially in the south of Marjah, the enemy is fighting from compounds where soldiers can very clearly see women or children on the roof or in a second-floor or third-floor window," he is quoted by Associated Press as saying.
"They are trying to get us to fire on them and kill the civilians."
As a result, his forces were having to make the choice either not to return fire, he said, or to advance much more slowly in order to distinguish militants from civilians.
Nato has stressed that the safety of civilians in the areas targeted in the joint Nato and Afghan Operation Moshtarak is its highest priority.
Journalist Jawad Dawari, based in Lashkar Gah, told BBC Pashto that Taliban fighters remained in many residential areas of Marjah and were defending their positions with heavy weapons.
"It is difficult for the Afghan army and Nato to storm Taliban-held areas because to do so may inflict heavy civilian casualties and there are still a lot of civilians in Marjah.
"Whenever they launch an attack, the Taliban take refuge in civilians' homes."
He had spoken to many local people in Marjah, he said, and they had all said the Nato offensive had made little progress since the first day.
An Afghan military official had told reporters that the backbone of the resistance came from foreign fighters - Pakistani and Arab - and that it was feared they might resort to suicide attacks, he added.
By Frank Gardner, BBC News, Kandahar
There's a lot of fighting going on in the Marjah area - the estimation of the number of insurgents there varies between 100 and 300. They are not all hardcore Taliban by any means. The US commander there, Brig Gen Larry Nicholson, said he thought about 80% were probably less committed local fighters hired to do this, as opposed to being hardcore, ideological jihadists.
The operation has taken a long time for a number of reasons - it's a big area, 200sq km, and they are having to cope with an unexpectedly large number of these IEDs. A lot of locals are telling the soldiers where the devices are but other IEDs are having to be defused very slowly.
The most senior US general in the south, Brig Gen Ben Hodges, gave the BBC a more upbeat assessment of Marjah, saying locals were coming out to give information on insurgents now that they were confident the forces involved in Operation Moshtarak were not leaving.
He said Afghan units would be staying for at least 30 days and the Marine battalions "for several months".
Speaking to the BBC after visiting Marjah, the commander of British forces in southern Afghanistan, Maj Gen Nick Carter, said the situation was dangerous, but that progress was being made.
He told the BBC's Frank Gardner it could take up to 30 days to clear the insurgents out, depending on when they lost the will to fight.
Troops taking part in the offensive have been having to deal with large numbers of improvised bombs.
American forces have found a so-called "daisy chain" - a long bomb rigged up from mortar bombs, rocket-propelled grenades and a motorbike, our correspondent says.
Nato has said that safeguarding civilians is its top priority
And British engineers have deployed a device called a "python" - a length of explosives designed to set off mines and clear a safe path through them, he says.
Afghan army chief of staff Besmillah Khan told the AFP news agency the threat from improvised bombs meant gains were coming "slowly".
Meanwhile, to the north, British forces have discovered an insurgent cache of stolen Afghan army and police uniforms.
The find suggests the Taliban could have been planning attacks disguised as Afghan security personnel, our correspondent says.
Nato says discussions with the local population on how to bring lasting security to the area are continuing, our correspondent adds.
Gen Hodges said several hundred police had been trained and would go into central Helmand once the situation was deemed appropriate.
British and Afghan troops are reported to be advancing more swiftly in the nearby district of Nad Ali than are their US and Afghan counterparts in Marjah.
Missiles 'on target'
Gen Carter confirmed on Tuesday a missile that struck a house outside Marjah on Sunday killing 12 people, including six children, had hit its intended target.
Afghan troops raise the national flag at a bazaar in Marjah
Gen Carter said the rocket had not malfunctioned and the US system responsible for firing it was back in use. Officials say three Taliban, as well as civilians, were in the house but the Nato soldiers did not know the civilians were there.
Initial Nato reports said the missile had landed about 300m (984ft) off its intended target. Gen Carter blamed these "conflicting" reports on "the fog of war".
Speaking on Tuesday, Dawud Ahmadi - a spokesman for Helmand Governor Gulab Mangal - said that 1,240 families had been displaced and evacuated from Marjah - and all had received aid in the provincial capital, Lashkar Gah.
Operation Moshtarak, meaning "together" in the Dari language, is the biggest coalition attack since the Taliban fell in 2001.
Allied officials have reported only two coalition deaths so far - one American and one Briton killed on Saturday.