KUNDUZ, Afghanistan (Reuters) - Hundreds of Taliban insurgents have launched an offensive to seize the northern Afghan city of Kunduz, which they captured and held for several days last year, provincial officials said on Friday.

Afghan forces prepare for battle with Taliban on the outskirts of Kunduz city, northern Afghanistan in this June 21, 2015 file photo. REUTERS/Stringer

The offensive around Kunduz began only days after the Islamist group announced their annual spring offensive, vowing to launch large-scale attacks using suicide bombers and guerilla fighters to drive the Western-backed government from power.

Fighting broke out on Thursday in six districts in Kunduz province, a crucial northern stronghold close to the Tajikistan border, as well as around the provincial capital, with Afghan security forces battling militants through the night.

“There is heavy fighting going on but the militants have failed to capture any areas and we are pushing them back,” Kunduz police chief Mohammad Qasim Jangalbagh told Reuters.

Taliban fighters briefly captured Kunduz city last year in a major blow to President Ashraf Ghani’s government. They also threatened to take Helmand province in the southern heartland of the insurgency after overrunning several districts.

With those memories still fresh, officials took to the airwaves to try to head off panic among the public.

“We will assure our people that the situation is under control and we will never allow the catastrophe that happened last year,” Jangalbagh said.

The insurgency has gained strength since the withdrawal of international troops from combat at the end of 2014 and the Taliban are stronger than at any point since they were driven from power by U.S.-backed forces in 2001.

The sound of gunfire and explosions could be heard as far as 5 km (3 miles) from the eastern outskirts of Kunduz city, witnesses reported. Fearful residents hid in their homes and many shops remained closed on Friday.

The highway between Kunduz and neighboring Takhar province was also blocked, officials said.

Imamuddin Qureshi, chief of Kunduz’s Imam Saheb district, said several security outposts had already fallen to insurgents and called on the government in Kabul to send reinforcements and air support immediately.

Outposts were also overrun in other districts and security forces fled to Kunduz city to regroup, Khanabad district chief Ayatullah Amiri said.

Taliban spokesman Zabihullah Mujahid said fighters had captured outposts in six districts and that three bomb blasts had killed seven members of the Afghan security forces just outside Kunduz. Those claims could not be verified immediately.

The brief capture of Kunduz last September was one of the biggest territorial gains made by insurgents since they were ousted from power.