Kabul, Afghanistan — The international charity Doctors Without Borders said at least 19 people, including 12 local staffers, were killed when its clinic came under "sustained bombing" Saturday in the northern Afghan city of Kunduz, where Afghan officials said helicopter gunships had returned fire from Taliban fighters sheltering in the facility.

The group said the facility, which was treating more than 100 patients, came under attack at 2:08 a.m. (2138 GMT). The charity did not say whether insurgents were present, and it was not immediately clear whether the staffers were killed by the Taliban, government or U.S. forces. The group said another 30 people were still missing after the incident.

The dead included seven patients from the intensive care unit, among them three children, it said. A total of 37 people were injured, including 19 staff members, and 18 patients and caretakers. Five of the injured staff members were in critical condition, it said.

Afghan forces backed by U.S. airstrikes have been battling the Taliban street-by-street in Kunduz since Thursday, to dislodge insurgents who seized the strategic city three days earlier in their biggest foray into a major urban area since the U.S.-led invasion of 2001.

The Ministry of Defense said "terrorists" armed with light and heavy weapons had entered the hospital compound and used "the buildings and the people inside as a shield" while firing on security forces. Brig. Gen. Dawlat Waziri, the ministry's deputy spokesman, told The Associated Press that helicopter gunships fired on the militants, causing damage to the buildings.

Interior Ministry spokesman Sediq Sediqqi said 10 to 15 "terrorists" had been hiding in the hospital at the time of the strike. "All of the terrorists were killed but we also lost doctors," he said. He said 80 staff members at the hospital, including 15 foreigners, had been taken to safety. He did not say what sort of strike had damaged the compound.

But Doctors Without Borders said "all indications currently point to the bombing being carried out international coalition forces." In a statement, the organization said the attack was a "grave violation of international humanitarian law" and demanded an independent investigation.

Army Col. Brian Tribus, a spokesman for American forces in Afghanistan, said a U.S. airstrike on Kunduz at 2:15 a.m. "may have resulted in collateral damage to a nearby medical facility" and that the incident was under investigation. He said it was the 12th U.S. airstrike "in the Kunduz vicinity" since Tuesday.

The Ministry of Defense said "terrorists" armed with light and heavy weapons had entered the hospital compound and used "the buildings and the people inside as a shield" while firing on security forces.

Doctors Without Borders said its trauma center "was hit several times during sustained bombing and was very badly damaged." At the time, the hospital had 105 patients and their caretakers, and more than 80 international and Afghan staff, it said.

AP video of the compound showed burning buildings with firearms — automatic rifles and at least one Russian-made machine gun — on the windowsills pointed outward.

Doctors Without Borders did not comment on the identities of the 30 missing people, but said all of its international staffers were alive and accounted for. It said it regularly updated its GPS coordinates with all parties to the conflict.

Fighting raged throughout the day, and at around 2 p.m., the Taliban seized the medical compound, according to Sarwar Hussaini, the spokesman for the provincial police chief. "Fighting is continuing between Afghan security forces and the Taliban," he said.

Taliban spokesman Zabihullah Mujahid had earlier issued a statement saying there were no Taliban fighters in the hospital at the time of the bombing. He also accused Afghanistan's intelligence service of deliberately directing airstrikes on the hospital.

Adil Akbar, a doctor at the trauma center who was on duty at the time, told The Associated Press that the operating theater, emergency room and other parts of the hospital complex had been hit in the bombing.

"I managed to escape after the attack but I know that most of the staff and even some of the patients are missing," he said.

Zabihullah Pashtoonyar, a former local radio reporter who was working as a security guard at the compound, was one of those killed in the incident, said his relative Gul Rahim.

Wahidullah Mayar, spokesman for the Public Health Ministry, tweeted that 37 people were wounded, among them 24 medical and non-medical staff.

Bart Janssens, the charity's director of operations, said "we do not yet have the final casualty figures," adding that the group's medical team was treating wounded patients and staffers.

Nicholas Haysom, the U.N. special representative in Afghanistan, condemned the "tragic and devastating airstrike" on the hospital. "Hospitals accommodating patients and medical personnel may never be the object of attack, and international humanitarian law also prohibits the use of medical facilities for military purposes."

The International Committee of the Red Cross, which also has facilities in Kunduz, said it was "deeply shocked." Amnesty International called for an investigation.

Doctors Without Borders, which operates in conflict zones across the globe, said it had treated 394 people wounded in fighting since the Taliban attacked the city. Afghan forces went in on Thursday, and the fighting has been underway since then.

Sediqqi said Afghan forces were still sweeping the city for militants, conducting "meter to meter, house to house operations" that would continue until "all those bad elements" had been eliminated.

The clinic in Kunduz is a sprawling facility with numerous buildings situated in the east of the city, in a residential area close to the local office of the NDS intelligence service.

Another Kunduz resident, Dawood Khan, said a cousin who works at the clinic as a doctor was lightly wounded in the bombing.

"I heard the sound of the bomb and rushed to the hospital to get news. The operating theater was on fire, people were terrified, running everywhere," he said.

Electricity and water have been cut off since the Taliban's Monday assault and seizure of the city, officials and residents said. Food and medical supplies cannot get through because the Afghan military is still working to clear mines planted by the Taliban. Sporadic gunfights are continuing in various pockets of the city as troops advance.

Most of the Taliban appear to have fled the city after the troops moved in on Thursday, taking looted vehicles, weapons and ammunition with them.

Officials have reported that they have moved east, into Takhar and Badakhshan provinces, where a number of districts fell to the Taliban on Friday. The Defense Ministry said troops had retaken the Baharak district after retreating under fire Friday.

The U.S. Embassy in Kabul issued an emergency notice to Americans in Badakhshan, saying they should "consider departing the area immediately."

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