Kabul, Afghanistan (CNN) Afghan security forces started retaking parts of Kunduz from the Taliban, officials said, one day after the key city had largely fallen in a major victory for the insurgents.

"A big military operation to clear all Kunduz city is about to start," Interior Ministry spokesman Sediq Sediqqi said Tuesday.

U.S. forces joined in the military action, launching an airstrike in Kunduz on Tuesday, said Brian Tribus, spokesman for U.S. forces in Afghanistan.

The Kunduz prison, a police compound and the neighborhood of Zir Dawra are among the areas Afghan forces have secured, Sediqqi said. The Taliban denied the prison and police facility had been secured by Afghan forces.

A day earlier, Sediqqi said Kunduz had largely fallen into "the hand of enemies." Kunduz is the largest city to be overrun by the Taliban since 2001.

Sayed Sarwar Hussaini, a spokesman for the Kunduz police chief, said Taliban insurgents seized the main roundabout in the city and made it to the prison, where they freed several hundred inmates. While Hussaini said 500 prisoners were freed, Rahmatullah Nabil, head of the National Directorate of Security, said the total was closer to 600. Of those, 110 prisoners were Taliban insurgents, Nabil said.

The Taliban also claimed to have seized a 200-bed hospital -- posting photos to social media that they claimed proved their control of the facility.

Also in Kunduz, the International Committee of the Red Cross reported that two of its vehicles had been "taken out of its offices in the city," but it did not say by who.

"Through its contact with all the relevant parties, the ICRC has been given reassurances that the vehicles would be returned in the near future," spokesman Zarlasht Sarmast said in an email.

Death toll rising

A public health official in Kunduz reported 170 civilian casualties in the fighting, including 16 people who were killed, according to journalist Sune Engel Rasmussen in Kabul. A Doctors Without Borders facility had admitted more than 100 injured people as of Monday, Rasmussen told CNN.

Photos: Taliban takes over Afghan city Photos: Taliban takes over Afghan city Afghan special forces prepare to launch an operation to retake the city of Kunduz, Afghanistan, from Taliban insurgents on Tuesday, September 29. The Taliban took control of most of the city the day before in its biggest victory since 2001. Hide Caption 1 of 5 Photos: Taliban takes over Afghan city A Taliban fighter sits on a motorcycle holding a Taliban flag in Kunduz on September 29. Hide Caption 2 of 5 Photos: Taliban takes over Afghan city Taliban fighters hug each other on September 29. Hide Caption 3 of 5 Photos: Taliban takes over Afghan city A Taliban fighter stands guard on a vehicle in Kunduz on September 29. Hide Caption 4 of 5 Photos: Taliban takes over Afghan city Taliban prisoners walk down a street after they were released by Taliban fighters from the main jail in Kunduz on Monday, September 28. Hide Caption 5 of 5

Sayed Sarwar Hussaini, a spokesman for the Kunduz police chief, said 83 Taliban militants have been killed, mostly in Afghan and coalition airstrikes.

Mawlawi Salam, the most senior commander of the Taliban in Kunduz, was killed, along with his deputy and 15 of their fighters in an airstrike, according to a statement from the National Directorate of Security.

"Afghan security forces will turn Kunduz into a great graveyard for the enemy," it read.

In the past 24 hours, 17 Afghan security forces have been killed and another 18 troops were wounded in fighting, acting defense minister Masoom Stanekzai said Tuesday afternoon. Stanekzai's toll was countrywide, not just in Kunduz, he said.

Photos: The Taliban Photos: The Taliban The Taliban, a Sunni Islamist organization operating primarily in Afghanistan and Pakistan, was formed in 1994. It was led by Mullah Mohammed Omar, a veteran of the Afghan mujahedeen that fought invading Soviets from 1979-1989. Omar, seen here in an undated video image, died in April 2013 , according to a representative for Afghan President Ashraf Ghani. Hide Caption 1 of 16 Photos: The Taliban In this image taken off television by BBC Newsnight, Omar -- fourth from left -- attends a rally with Taliban troops before their victorious assault on Afghanistan's capital, Kabul, in 1996. The Taliban's aim is to impose its interpretation of Islamic law on Afghanistan and remove foreign influence from the country. Most of its members are Pashtun, the largest ethnic group in Afghanistan. Hide Caption 2 of 16 Photos: The Taliban Tanks manned by Taliban fighters are decorated with flowers in front of the presidential palace in Kabul on September 27, 1996. Hide Caption 3 of 16 Photos: The Taliban Taliban soldiers in Russian-made tanks fire on the forces of former Afghan defense minister Ahmad Shah Massood in October 1996. Hide Caption 4 of 16 Photos: The Taliban Afghan women in Kabul are covered head to toe in traditional burqas on October 16, 1996. After taking over Kabul, the ruling Taliban imposed strict Islamic laws on the Afghan people. Television, music and non-Islamic holidays were banned. Women were not allowed to attend school or work outside the home, and they were forbidden to travel alone. Hide Caption 5 of 16 Photos: The Taliban Three women hitch a ride on the back of a donkey cart as they pass by the ruins of Kabul's former commercial district in November 1996. Hide Caption 6 of 16 Photos: The Taliban This is an undated image believed to show the Taliban's former leader, Mullah Mohammed Omar. In 1997, the Taliban issued an edict renaming Afghanistan the Islamic Emirate of Afghanistan. The country was only officially recognized by three countries: Pakistan, Saudi Arabia and the United Arab Emirates. Hide Caption 7 of 16 Photos: The Taliban In 1997, Omar forged a relationship with al Qaeda leader Osama bin Laden, pictured. Bin Laden then moved his base of operations to Kandahar, Afghanistan. Hide Caption 8 of 16 Photos: The Taliban In March 2001, Taliban soldiers stand at the base of the mountain alcove where a Buddha statue once stood 170 feet high in Bamiyan, Afghanistan. The Taliban destroyed two 1,500-year-old Buddha figures in the town, saying they were idols that violated Islam. Hide Caption 9 of 16 Photos: The Taliban After the 9/11 attacks, the United States conducted military strikes against al Qaeda training camps and military installations of the Taliban regime. In this long-exposure photo, a U.S. Navy fighter jet takes off from the deck of the USS Enterprise on October 7, 2001. Hide Caption 10 of 16 Photos: The Taliban An Afghan anti-Taliban fighter pops up from his tank to spot a U.S. warplane bombing al Qaeda fighters in the Tora Bora region of Afghanistan on December 10, 2001. After massive U.S. bombardment as a part of Operation Enduring Freedom, the Taliban lost Afghanistan to U.S. and Northern Alliance forces. Hide Caption 11 of 16 Photos: The Taliban Afghans look into Omar's bedroom as they go through his compound on the outskirts of Kandahar on December 11, 2001. Hide Caption 12 of 16 Photos: The Taliban In April 2011, hundreds of prisoners escaped from a prison in Kandahar by crawling through a tunnel. The Taliban took responsibility for the escape. This picture shows a general view of the prison, top center, and the house, bottom right, from which Taliban militiamen dug the tunnel leading to the prison. Hide Caption 13 of 16 Photos: The Taliban Security guards stand outside the new Taliban political office in Doha, Qatar, before its official opening in June 2013. The Taliban announced that they hoped to improve relations with other countries, head toward a peaceful solution to the Afghanistan occupation and establish an independent Islamic system in the country. Hide Caption 14 of 16 Photos: The Taliban Zafar Hashemi, deputy spokesman for Afghan President Ashraf Ghani, speaks during a news conference on July 29, when the news of Omar's death was announced. Hide Caption 15 of 16 Photos: The Taliban Mullah Akhtar Mohammad Mansour became the leader of the Taliban after Omar's death. Mansour was killed in an airstrike in Pakistan on Saturday, May 21, 2016 Hide Caption 16 of 16

Afghan President Mohammad Ashraf Ghani repeated the claim that security forces had retaken control of the prison and the police headquarters. How long it would take to regain control of the rest of the city -- a task made more difficult as Taliban fighters hid among civilians -- was unclear, he said.

In a statement recounting his news conference from the presidential palace, Ghani said reinforcements, including an army battalion, special forces and commandos had arrived in Kunduz, and "the city is in the process of being cleared of terrorist groups."

"The problem is that the treacherous enemy is using civilians as shields," he said. "The Afghan government is a responsible government so it cannot carry out airstrikes on a city and on the houses of its people."

Coordination among security forces has improved, he said, adding that "they are prepared to give any sacrifice to frustrate the attempts of the enemies of the people of Afghanistan who want to disrupt security on orders of others."

A big prize

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For months, the Taliban was eyeing Kunduz and bolstered its strength north of the city before moving in.

Kunduz is the capital of Kunduz province, an affluent area in northern Afghanistan known for its trade ties. The main route to Tajikistan also runs through Kunduz province.

Afghan Chief Executive Abdullah Abdullah told CNN's Christiane Amanpour that initial reports suggest the Taliban were able to infiltrate, rather than fight their way into, the city.

"The whole focus is on how to retake it and hold those positions," he said.

The release of 500 to 600 prisoners by the Taliban makes the security situation in the city even more challenging.

One of the newly released prisoners spoke to CNN.

"We were hearing gunshots throughout the day, but it was 4 p.m. when the Kunduz prison guards left the compound. Then, the inmates broke all the doors and fences and started running toward the main gate," he said.

"As soon as we opened the main gate, we saw a group of armed Taliban outside the gate. They told us that we were free and could go home. ... We all headed towards our homes."