Taliban fighters seized a district center in northern Afghanistan on Saturday, reports said.

“Fighters captured the governor’s house and police headquarters in Aq Tapa, in the Qala-e Zal district of Kunduz province and Afghan government forces were fighting to drive them out,” Reuters quoted Sayed Assadullah Sadat, a provincial council member, as saying.

The Taliban’s main spokesman Zabihullah Mujahid said fighters had captured a police headquarters, 10 security check posts and a market in Qala-e Zal, north of Kunduz city.

At the other end of the country, in Helmand, insurgents launched a vehicle bomb attack on a military base in Nad Ali district, killing four civilians and a soldier, according to a statement from the provincial governor’s office.

The Taliban announced the official start of their annual spring offensive this week, continuing the heavy fighting seen across Afghanistan recently as warmer weather has set in.

Assessments of the size of Taliban territorial control vary but the Pentagon estimates that 56 percent of the country is under government control, while a BBC survey this year estimated the insurgents were active in 70 percent of Afghanistan.