The Taliban launched a large-scale attack on Kunduz, one of Afghanistan's main cities, killing at least 15 people and wounding more than 75 others, government officials said Saturday, even as the insurgent group continued negotiations with the United States on ending America's longest war.

The militants, who have demanded that all foreign forces leave Afghanistan, now control or hold sway over roughly half of the country and are at their strongest since their 2001 defeat by a US-led invasion. Such attacks are seen as strengthening their negotiating position.

The US envoy in the talks, Zalmay Khalilzad, said in a Twitter post that he raised the Kunduz attack with the Taliban and told them “violence like this must stop.” He is expected to visit Kabul on Sunday to brief the Afghan government.

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A suicide bomber detonated his explosives at the main intersection in Kunduz after hours of efforts by Afghan security forces to push the militants into the city's outskirts, provincial council member Ghulam Rabani Rabani told The Associated Press. The blast killed 10 people and wounded five others, Interior Ministry spokesman Nasrat Rahimi said.

The Taliban quickly claimed responsibility for the bombing, which occurred after the defense and interior ministers visited Kunduz and asserted that Afghan forces had repelled the attackers. The commander of US forces in Afghanistan, Gen Scott Miller, also visited the city, Khalilzad said.

Afghan officials confirmed casualties among security forces in the day of fighting but did not say how many and said at least 60 Taliban fighters had been killed. As night fell, they said gun battles continued on the outskirts of Kunduz, a strategic crossroads with easy access to much of northern Afghanistan as well as the capital, Kabul, about 200 miles (335 kilometres) away.

Presidential spokesman Sediq Seddiqi told reporters the attack was “completely against the peace talks.”

The bodies of at least three civilians and two members of the security forces were taken to the Kunduz hospital earlier in the day and at least 80 wounded civilians of all ages were treated, including women and children, said the provincial health director, Esanullah Fazeli.

Rabani said the insurgents briefly took control of the hospital, but Fazeli said the fighters left after staffers told them the patients could be hurt in any cross fire.

“In a way we are thankful that the Taliban accepted what they were told,” he said.

The Taliban launched their attack from several points around Kunduz overnight, officials said. Hours later the Afghan defense minister, Asadullah Khalid, rejected speculation that the city had collapsed.

The Taliban have continued bloody assaults on civilians and security forces even as their leaders meet with Khalilzad in Qatar to negotiate an end to nearly 18 years of war.

Talks continued Saturday, and Afghanistan's chief executive, Abdullah Abdullah, said Khalilzad would visit Kabul on Sunday to brief the government. Both the US and Taliban in recent days have signaled they are close to a deal.

One Afghan analyst, former deputy interior minister Mirza Mohammad Yarmand, said the attack on Kunduz showed the Taliban are not interested in a cease-fire, which has been a key issue in the Qatar talks.

The United States in the negotiations has also sought Taliban guarantees that Afghanistan will no longer be a launching pad for terror attacks such as the September 11, 2001, attack on the US by Al Qaeda. The Taliban government had harbored Al Qaeda leader Osama bin Laden.

Some 20,000 US and NATO forces remain in Afghanistan after formally ending their combat role in 2014. They continue to train and support Afghan forces fighting the Taliban and a local affiliate of the militant Islamic State group.

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Many Afghans worry that an abrupt departure of foreign troops will leave Afghan forces vulnerable and further embolden the Taliban, who already portray a US withdrawal as their victory.

“We have lost the city in the past and know the Taliban can attack again from insecure areas,” a lawmaker from Kunduz, Fatima Azizi, told the local Ariana television channel on Saturday.

“Unfortunately, civilians are again the victims,” she said.

The Taliban seized Kunduz, at the heart of a major agricultural region near Tajikistan, for around two weeks in 2015 before withdrawing in the face of a NATO-backed Afghan offensive. The insurgents pushed back into the city centre a year later, briefly raising their flag before gradually being driven out again.