Nasir Wakif / Reuters Afghan security forces keep watch in front of their armored vehicle in Kunduz city, Afghanistan on October 4, 2016.

KABUL, Oct 4 (Reuters) - Afghan forces regained control of most of the northern city of Kunduz on Tuesday amid sporadic fighting, officials said, as questions arose over how Taliban militants once again managed to penetrate the city’s defenses.

The U.S. military in Kabul said that a “robust” group of special forces, as well as aircraft, were positioned near the city to provide support to Afghan soldiers should the need arise.

Insurgents slipped past government forces early on Monday and occupied or attacked central areas of Kunduz, almost exactly a year after they briefly captured the city in one of their biggest successes of the 15-year war.

Social media accounts linked to the Taliban, which taunted Afghan forces and their Western backers throughout Monday’s attack, said fighters were still inside Kunduz on Tuesday, with “clashes ongoing” and government troops “on the run.”

The attack in Kunduz, along with Taliban gains in areas of Helmand and Uruzgan where they also threaten provincial capitals, has underlined the group’s growing strength and exposed weaknesses in Afghanistan’s defenses.

Government representatives are meeting international donors in Brussels this week to try to secure billions of dollars in additional aid.

Nasir Wakif / Reuters An Afghan National Army (ANA) soldier sits in front of a closed shop in the downtown of Kunduz city, Afghanistan on October 3, 2016.

DID POLICE RUN AWAY?

Questions dogged Afghan security forces on Tuesday, with the U.S. military reporting it saw little evidence of significant fighting as the Taliban moved in.

Some witnesses said many police had abandoned checkpoints without firing a shot, a month after a similar scene played out during a Taliban raid on the provincial capital of Uruzgan province, Tarin Kot.

“The police did not fight yesterday,” said Commander Ali, a local militia chief who, like many Afghans, only goes by one name. “Some fought in a few places, but a majority of them escaped without any resistance.”

He estimated that about 200 Taliban attackers quickly sent thousands of security personnel, mostly police, fleeing to the army base near the city’s airport.

That account was supported by another local police commander, who said senior leadership had failed to back up those police officers who did fight, while the army arrived after the fact.

“At some checkpoints police fought well, but they did not get reinforcement,” said the commander, who spoke on condition of anonymity as he was not authorized to speak publicly.

In Washington on Monday, Pentagon spokesman Captain Jeff Davis told reporters the Taliban attack was more of a “Western-movie style shoot-them-up” raid than a concerted military offensive.

Afghan Defence Ministry spokesman Dawlat Waziri said no checkpoints held by army troops had been abandoned.

Afghan officials are investigating how the Taliban managed to push into the city’s center, despite months of military operations aimed at preventing a repeat of last year’s debacle, Ministry of Interior spokesman Sediq Sediqqi told reporters in Kabul.

“Right now we are focusing on clearing the city,” he said.

Nasir Wakif / Reuters Afghan security forces keep watch in front of their armored vehicle in Kunduz city, Afghanistan on October 4, 2016.

FIVE AFGHAN SECURITY PERSONNEL KILLED

Residents blamed ethnic and political divisions within the city’s leadership for the failure of local security forces to prevent the Taliban raid.

There is a culture of impunity for police and other armed forces that are often more loyal to local strongmen than to the central government, the second police commander said.

Much of the effort to push the Taliban out of the city was led by elite Afghan military and police special forces, many of whom arrived from other cities.

Backed by U.S. special forces and air support as well as warplanes of their own, Afghan soldiers sought to clear the city overnight, said Kunduz police chief Qasim Jangalbagh.

Taliban fighters, seeking to reimpose strict Islamic law after their 2001 ouster, remained in several areas of Kunduz, but Afghan forces had made progress, he added.

“We have received reinforcements and have air support. More then 25 enemies are killed so far and we have retaken several places. We are committed to clear the city.”

Five members of government security forces had been killed, with another 13 wounded, Waziri of the defense ministry said.

Overnight, a U.S. helicopter conducted an air strike “to defend friendly forces,” the U.S. military command in Kabul said.

(Reporting by Afghanistan bureau; Writing by Josh Smith; Editing by Mike Collett-White and Nick Macfie)