The escapees appear to have been reinforced by militants who are infiltrating the area using canals, trees, and vineyards as cover.
The militants are thought to have concentrated in several villages of the Arghandab district, north of Kandahar city. Ahmed Wali Karzai, the head of Kandahar's provincial council and the brother of Afghan President Hamid Karzai, told RFE/RL's Radio Free Afghanistan that at least one-third of the militants have come from other countries.
"According to credible sources, if you look at all of the 500 or 600 Taliban fighters in this battle, about [one-third] are foreigners," Karzai said. "They are not from Afghanistan. They are from different places -- Arabs, Chechens, Chinese, and people from [Pakistan's] tribal regions of [North or South] Waziristan."
The brother of the Afghan president says the Taliban fighters are thought to include some of the hundreds of suspected Taliban who escaped from a prison in Kandahar on June 13 with the help of a bold attack by militants.
General Carlos Branko, a spokesman for NATO forces in Afghanistan, told Radio Free Afghanistan on June 18 about the unfolding battle in the area.
"This operation in Arghandab [district] that commenced this morning is part of an overall operation in Kandahar Province," Branko said. "The Afghans are in the lead and supported by [troops from ISAF, the International Security Assistance Force]. This is very important because the Afghan National Army is demonstrating a high capability to conduct and to lead operations. So far, we have not seen large numbers of insurgents. There is only minor contact. But this does not mean there are no insurgents present."
Dawa Khan Minapal, a Radio Free Afghanistan correspondent in Kandahar Province, traveled to a government checkpoint to the north of the city of Kandahar that is on the edge of the battle zone. He described a battle scene in the Arghandab Valley on June 18 in which NATO aircraft searched for Taliban fighters.
"NATO helicopters and fixed-wing aircraft have been flying over the area all morning," Minapal said. "I can hear the sound of heavy weapons firing and the sound of machine guns in the distance. Villagers are still fleeing the fighting, trying to evacuate the area. They were warned in the previous days to evacuate. As the helicopters and fighter jets fly over, I can see two targets that they have been bombing. And I hear the sound of heavy explosions in the area."
Minapal says Afghan and NATO ground troops have set up blocking positions and are moving cautiously toward a series of villages where the Taliban are thought to have fortified themselves.
Destroyed Bridges, Planted Mines
The Arghandab district is divided into northern and southern areas by the Arghandab River. Minapal said the Taliban are now positioned to the south of the river, while government and coalition forces are on the north side. He said the Taliban have destroyed small bridges over irrigation canals in the area and have been planting land mines.
Taliban fighters are thought to be moving into the Arghandab Valley from the Panjwai and Khakrez districts, which are famous as Taliban strongholds, Minapal said. There also is a large hydroelectric dam on the river -- the Arghandab Dam -- that provides electricity to residents in the area. He said the vegetation in the valley and the irrigation canals provide cover for guerrilla fighters, making it easier for Taliban fighters to move in from other districts.
Some 400 Taliban prisoners escaped from a jail in Kandahar on June 13 with the help of a bold attack by militants outside of the facility.
Ahmed Wali Karzai, the head of Kandahar's provincial council and the brother of Afghan President Hamid Karzai, told RFE/RL that many of the besieged Taliban fighters are thought to be escaped prisoners. But he says they also have received reinforcements from other militants.
Villagers who have fled areas now under Taliban control say many of the Taliban reinforcements appear to be from Pakistan's tribal regions because they are wearing clothes and "pakol" hats from that region instead of the turbans worn by local Taliban.
There were no immediate reports on casualties among Afghan and NATO troops in the battle. But Afghan officials claim they killed 16 to 25 Taliban fighters during their initial strikes on June 18.
Radio Free Afghanistan correspondent Freshta Jalalazai contributed to this report from Prague