KABUL, Afghanistan (AP) — The new leader of the Afghan Taliban boasted in a phone call with The Associated Press on Friday that the group's three-day occupation of the northern city of Kunduz was a "symbolic victory" demonstrating the insurgents' strength, even as his fighters were fleeing under fire from Afghan government troops.

The Taliban takeover of Kunduz was an embarrassing blow to the government of President Ashraf Ghani, which was trying to determine how a force of several hundred insurgents were able to cause the collapse of several thousand troops defending the city.

Still, in the end, the Taliban were unable to hold their ground as the Afghan military rallied in a counterattack, a sign of how the insurgents lack the manpower or firepower to carry out much more than short-term sorties into large urban areas.

The dramatic Taliban assault on Kunduz, a city of some 300,000 — and the boasts of Mullah Akhtar Mansoor — appeared aimed in part at boosting Mansoor's legitimacy as leader in the face of opponents within the movement. He was formally elevated to the post in August, after the Afghan government revealed that longtime Taliban leader Mullah Mohammed Omar had died two years earlier.

His appointment caused a large public rift in the Taliban, whose leadership is said to be based in neighboring Pakistan, when Mullah Omar's family objected to him as leader. Though they later rallied behind Mansoor, some factions are yet to be convinced. The takeover of Kunduz was reportedly run by one of Mansoor's own appointees, Mullah Abdul Salam, which could help shore up his legitimacy.

Mansoor spoke to the AP by telephone from an unknown location.

"The victory is a symbolic victory for us," he said. "Moreover, it is also a historical event which will be remembered."

"People who said we were a small force with an unchosen leader can now see how wrong they were about the potential and strength my people have," he said.

As he spoke, Taliban gunmen were still leaving Kunduz after what residents said was a spree of looting government offices and international charities, and terrorizing citizens as they went house to house looking for civil servants and human rights defenders. The U.N. said around 6,000 people had managed to flee the city before militants closed off most exits.

The insurgents took the city on Monday after a multi-front surprise attack. They quickly sealed and mined roads to prevent anyone coming or going, and while some fighters fought a long gun battle in a failed attempt to take the airport, others went on the rampage, stealing cars — including armored vehicles from the U.N. and the International Committee of the Red Cross — and torching buildings. A statement from Ghani's office accused the Taliban of committing "rape, torture and murder" in the city, without offering details on the allegations. Amnesty International and the U.N.'s representative in Afghanistan, Nicholas Haysom, have also cited reports of extrajudicial killings and kidnappings.

Government forces moved in early Thursday, backed by U.S. airstrikes, and have reclaimed control over much of the city. Sporadic battles were still being fought Friday as a combined force of Afghan army and police sought to eliminate pockets of insurgents.

Sixty people were killed and around 400 wounded in the fighting since Monday, the spokesman for the Ministry of Public Health, Wahidullah Mayar, wrote on his Twitter account, apparently referring to civilians. The government claimed 200 Taliban were killed, a claim Mansoor called a lie.

Officials, residents and aid workers reported growing shortages of food and medicines. Water and electricity were cut off, and most businesses shuttered.

"We urgently need medical supplies because the battle is still going on and so we expect more casualties," said Saad Mukhar, head of the city's public health department, adding that supplies sent from Kabul were being held up on the way.

The ICRC said it had supplies ready to be flown into Kunduz as soon as the airport reopened. "Medical staff in the city cannot get to the hospitals because of the on-going fighting," Kunduz-based doctor Peter Esmith Ewoi said in an ICRC statement.

Even if the occupation was brief, Kunduz was the first provincial capital and major urban area the Taliban have taken in their campaign against the Kabul government, waged since their own rule was toppled in the 2001 U.S.-led invasion.

That made it a humbling defeat for Ghani and raised questions over whether the U.S.-trained military was capable of defending the country now that most coalition forces have withdrawn.

Ghani has launched an investigation into how the Taliban, with only a few hundred gunmen, could have overwhelmed the city defended by a few thousand government troops.

Meanwhile, the Taliban appeared to be taking advantage of a security void elsewhere as Afghan troops from neighboring provinces redeployed to Kunduz. Taliban attacks forced government troops to withdraw from two districts in Badakhshan province, the provincial governor's spokesman Ahmad Nawid Frutan said, and there was further fighting in Takhar province. Both provinces are to the east of Kunduz.

Michael Semple, professor at the Institute for the Study of Conflict, Transformation and Justice at Queen's University in Belfast, said the Taliban attack on Kunduz aimed to loot vehicles, weapons and ammunition. But he said the battle should be a warning to Ghani that the Taliban have the battlefield discipline to plan and execute such operations.

"Ghani needs to take them seriously," Semple said.

The city's seizure rattled many in Afghanistan, concerned that the Taliban's expanding footprint could mean they are gearing for a more intense war with Afghan troops. Before this year's summer fighting season began, Afghanistan's northern region was not known for a strong Taliban presence, unlike the south and east. Kunduz sits on lucrative smuggling routes for drugs, minerals and weapons to and from Central Asia.

Despite a fierce summer of fighting across the country, during which they have taken control of small towns and rural districts alike, the Taliban have quickly buckled under counter-offensives from Afghan forces.

Mansoor is also likely to use the Kunduz operation to push a more populist image of the Taliban, remembered for their extremist interpretation of Islam and brutality under Mullah Omar.

Mansoor claimed the success in Kunduz countered Afghan government pronouncements "that the people of Afghanistan are against the Taliban and want to rid them from their country."

He said his fighters in Kunduz had tactically avoided residential areas and civilian casualties.

"We were making sure to cause minimum civilian casualties but then the police forces and government security forces, to hide their shameful defeat, started to open fire on everyone, not caring if they were killing the Taliban or innocent civilians," Mansoor said.

Mansoor warned of more Taliban operations like Kunduz.

"We are hoping to hit this government harder every time and win back our land from these tyrants," he said.

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Khan reported from Kandahar, Afghanistan. Associated Press writers Amir Shah and Humayoon Babur in Kabul, Afghanistan, contributed to this report.