KABUL, Afghanistan — After months of ferocious fighting, Afghan army units battling the Taliban in southern Helmand province are facing major restructuring and leadership changes, with several key commanders being replaced, a U.S. military official said Monday.

Helmand has been a fierce battleground since last fall, with fighting taking place in 10 districts. At times, the insurgents have laid siege on army bases and threatened to overrun large chunks of territory. Local officials have called for help from central authorities and complained publicly over corruption that includes syphoning off salaries, food, fuel and equipment.

U.S. Army Brig. Gen. Wilson Shoffner, the head of public affairs for the U.S.-NATO mission, told The Associated Press that the Afghan army corps in Helmand is now being "rebuilt" and that senior officers are being replaced.

The reasons for the changes in the Afghan army's 215 Maiwand Corps "are a combination of incompetence, corruption and ineffectiveness," Shoffner said. The corps' commander has been replaced, along with "some brigade commanders and some key corps staff up to full colonel level," he said.

Helmand is a strategic region for the Taliban, as it as it shares a border of more than 250 kilometers (155 miles) with Pakistan. It grows large quantities of opium, used to produce most of the world's heroin. The harvest is worth up to $3 billion a year, and helps fund the insurgency.

The Afghan Defense Ministry confirmed the changes in Helmand. It said veteran army Gen. Moheen Faqiri was appointed to lead the corps and took over two months ago.

Gen. Dawlat Waziri, the ministry's spokesman, said brigade commanders have also been rotated out and replaced.

"Soon, other army units will have new commanders there," Waziri said.

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In October, a meeting of the National Security Council discussed the worsening situation on the ground. In the presence of President Ashraf Ghani and U.S. Army Gen. John F. Campbell, commander of U.S. and NATO forces in Afghanistan, the NSC heard that Afghan security forces were badly led, poorly equipped and in the previous three months had suffered 900 casualties, including 300 dead.

Minutes of the Oct. 29 meeting, obtained by the AP, show that Helmand was described by the former head of the intelligence agency, Rahmatullah Nabil, as "the biggest recruiting pool for the Taliban" and the insurgents' "primary source of revenue" from poppy for heroin and marble smuggling.

Another concern is the Afghan police who are fighting on the front-lines across Helmand, often without the equipment and backup of the army, which means casualties are higher.

Last Wednesday, Gen. Abdul Rahman Sarjang, the Helmand provincial police chief, said the Afghan security forces were "exhausted" and in dire need of reinforcements. He also told the AP that a lack of coordination between the army and police was hampering progress in the fight.

The Taliban have made serious stands in seven Helmand districts — Sangin, Gereshk, Khanashin, Musa Qala, Nawzad, Washer and Marjah — and at least three districts of Lashkar Gah are also under threat, Sarjang said.

The changes in Helmand reflect that Afghanistan's civilian and military leaders are learning the limitations of the security forces as they take on the Taliban alone following the drawdown of the international combat mission at the end of 2014. The U.S. and NATO maintain 13,000 troops in Afghanistan, mostly in an advisory and training capacity.

In a most serious illustration of the dire battlefield situation in Helmand, the district of Sangin was besieged for weeks and in late December fears escalated that it would completely fall to the insurgents. The United States conducted airstrikes on Taliban positions, the British rushed special forces advisers to the area, and the Afghan military dropped food and ammunition to soldiers and police who were surrounded in their base.

Nabil told the NSC meeting there were about 12,000 Taliban fighters in Helmand, up to 60 percent of them from other parts of the country — evidence the insurgents had reinforced their numbers for the fight. Nabil also said Afghan forces' morale was "extremely low" and discipline had broken down with "junior commanders openly defying their superiors."

"Helmand is in a crisis," Nabil told the meeting.

Shoffner, the U.S. general, said troops had been moved from other parts of the country to reinforce Helmand and that strategies have to change.

The notion that there is a "fighting season is outdated," he said, as the Taliban offensives — which in the past occurred in the warmer, summer months — have escalated even in colder weather.

NATO officials have told the AP that Afghan troops have taken huge casualties — 28 percent higher in 2015 than before the international combat mission ended, according to reports received by the international coalition. The officials spoke on condition of anonymity because they were not authorized to discuss the reports.

Afghan authorities do not release the casualty tolls for their combat forces. In 2014 that figure was estimated to have been about 5,000.

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Associated Press writer Rahim Faiez in Kabul, Afghanistan, contributed to this story.