KUNDUZ CITY: Taliban fighters battled their way into the centre of Kunduz city in northern Afghanistan on Monday and seized the provincial governor's office, in one of the militants' biggest territorial gains in 14 years of war, witnesses and officials said. The insurgents raised the white Taliban banner over the central square and freed hundreds of fellow militants from the local jail, in a major setback for Afghan forces who abandoned a provincial headquarters for the first time since 2001.

The stunning assault came a day before President Ashraf Ghani's unity government marked its first anniversary, and will further complicate efforts to resume stalled peace negotiations. It was the second time this year that the hardline Islamist movement has besieged Kunduz city, defended by Afghan forces battling largely without NATO's support after it withdrew most of its troops last year.

The insurgents launched a surprise, three-pronged offensive before dawn, and by evening they had captured the governor's compound and provincial police headquarters, said Zabihullah Mujahid, spokesman for the hardline Islamist movement. "Our fighters are now advancing towards the airport," Mujahid said on his Twitter account. Ministry of Interior spokesman Sediq Sediqqi later confirmed that "most of Kunduz city has fallen to the Taliban", and said Afghan forces were regrouping at the airport.

The Kunduz assault marks a troubling development in the insurgency, although Afghan forces have managed to drive the Taliban back from most of the territory they have gained this year during an escalation in violence. "It is certainly the first major breach of a provincial capital since 2001," said Graeme Smith, senior analyst for International Crisis Group. "They are choking the Afghan forces from all sides. It looks pretty grim." The United Nations Assistance Mission in Afghanistan evacuated its Kunduz compound on Monday morning, soon after the assault began. "They've been relocated within Afghanistan," said UN spokesman Dominic Medley, declining to say where or how many staff were evacuated.

Afghanistan's deputy chief of army staff, Murad Ali Murad, defended the Afghan security forces' performance, suggesting they withdrew to avoid harming civilians with all-out urban warfare. "There were enough troops inside Kunduz city, but the insurgents used some route deemed not that sensitive," Murad told a news briefing late on Monday. "Our forces arrived there on time, but we had to take extra care not to cause civilian casualties." Dozens of Afghan special forces were flown to Kunduz airport on a C-130 aircraft and were preparing to launch a counter-attack. Abdullah Danishy, deputy governor of Kunduz, vowed that Afghan forces would retake the occupied city. "We have reinforcements coming from other areas and will beat back the Taliban," Danishy said by telephone from Kunduz airport.

But with most of downtown Kunduz now in Taliban hands and terrified civilians either trying to flee or hiding inside their homes, the insurgents may be tough to dislodge. "Once they get inside an urban area, your air assets and artillery become much less useful," Smith said.

One Reuters witness saw buildings on fire in the south of the city and Taliban fighters entering a 200-bed government-run hospital. Dozens of panicked residents fled to the city's main airport but were turned away by security forces. "My uncle's wife has been killed by the Taliban today and still my wife and kids are in the area that the Taliban captured, so it is important to free my family," said Matin Safraz, an official at the interior ministry who was visiting Kunduz for the Muslim holiday of Eid. Taliban spokesman Mujahid urged Kunduz residents to stay inside. "The mujahideen are trying to avoid any harm to Kunduz residents," he said.