KUNDUZ - Afghan security forces drove Taliban fighters back from Kunduz city Friday, officials said, as the insurgents began the 2016 fighting season by targeting the northeastern provincial capital they briefly captured last year.

Fighting took place within city limits as well as in six provincial districts, Kunduz governor Asadullah Omarkhil said in a video statement. “Fortunately they have faced defeat by the Afghan security forces,” he said, adding that 30 insurgents were killed and 20 wounded within the city’s limits. “At the moment, the security situation is absolutely normal,” he said.

“They dreamed of capturing the city of Kunduz, but they faced a jaw-breaking answer from Afghan forces .”

The Taliban left security forces reeling with their brief takeover of Kunduz late last year, their biggest victory since they were toppled from power in 2001.

On Tuesday the insurgents announced the start of the “spring offensive” even as the government in Kabul tries to bring them back to the negotiating table to end the drawn-out conflict.

Shir Aziz Kamawal, a police commander in charge of Kunduz province, confirmed that fighting had taken place in six districts Friday, saying the insurgents had “failed” but that fighting was ongoing.

A Taliban spokesman said security forces had “fled” the districts. The insurgents are known to regularly exaggerate their battlefield claims.

The annual spring offensive normally marks the start of the “fighting season”, though this winter the lull was shorter and the Taliban continued to battle government forces albeit with less intensity.

The Taliban’s resurgence has raised serious questions about Afghan forces’ capacity to hold their own, with an estimated 5,000 troops killed last year, the worst ever toll.

Peace talks which began last summer were abruptly halted after it was revealed that Taliban leader Mullah Omar had been dead for two years.

A four-country group comprising Afghanistan, the United States, China and Pakistan has been holding meetings since January aimed at jump-starting negotiations, though their efforts have so far been in vain.

Meanwhile, Afghan aircraft killed more than 40 fighters loyal to Islamic State in a raid in the eastern province of Nangarhar, officials said on Friday.

Although casualty claims by all sides are difficult to verify, Thursday's operation appears to have been an unusually large strike by Afghanistan's fledgling air force, which has been building up its capacity since the withdrawal of the NATO-led coalition from most combat operations in 2014.

"Based on our intelligence, the Afghan air force carried out the strike and killed more than 40 Daesh fighters," Khogyani told Reuters, using a common Arabic acronym for Islamic State.

He said the militants had gathered to launch attacks in Nangarhar, bordering lawless areas of Pakistan.

The Afghan army public relations directorate said 42 IS militants had been killed in a joint operation in Nangarhar and a training centre destroyed. It said the Afghan air force had carried out 83 fighting operations around the country, causing heavy casualties to both the Taliban and IS.

Forces inside Afghanistan allied to Islamic State, whose core territory covers swathes of Syria and Iraq, have stepped up attacks against the much larger Afghan Taliban movement in pockets of the country's east.

In the past few months, the US fighter planes have also struck against Islamic State fighters in Nangarhar, forcing dozens to relocate to the rugged mountain terrain of the neighbouring province of Kunar.

A US military spokesman said the United States has carried out 70 to 80 air strikes against Islamic State in Afghanistan in the three months since the US forces were given broader authority to target militants in January.

Although Afghan forces still depend heavily on US air power for both logistics and close combat support, the local air force has been building up its strength as more pilots and air crew qualify and more aircraft are delivered.

As part of its buildup, the air force took delivery of a first batch of A-29 Super Tucano attack aircraft in February.

The A-29 took part in their first independent operation in the northern province of Badakhshan on Thursday, and the Afghan air force was steadily improving targeting and approvals to minimize civilian casualties, the new commander of the NATO-led coalition in Afghanistan, US General John Nicholson said.

"It's much more than just the pilot being able to fly the plane and release the ordnance, there's a whole system that surrounds this," he told Reuters in an interview this week.