Hundreds of Taliban fighters launched a brazen attack on the northeastern Afghan city of Kunduz on Monday, trading heavy fire with police and soldiers in their third attempt this year to capture the provincial capital.
The siege came a day after a bomb attack on a volleyball match killed 13 and the Islamic State group carried out coordinated strikes against police in the country's east, ending a brief lull in violence during the Muslim festival of Eid.
"The Taliban launched an attack on Kunduz city from several directions," Kunduz provincial police spokesman Sayed Sarwar Hussaini told AFP.
"So far 20 Taliban insurgents were killed in the fighting in different parts of Kunduz, and four Afghan security forces were confirmed wounded," Hussaini said.
"Right now, heavy fighting is ongoing between our forces and the Taliban in Khanabad, Char Dara and Imam Sahib, the main entrances into the city of Kunduz," he said, adding that "security forces are repelling" the militants.
Earlier the Taliban had seized several security checkpoints near the city, an AFP journalist in Kunduz said, though it was unclear if they had held on to their gains.
The city's streets were deserted as residents barricaded themselves indoors.
"The situation is very bad. The fighting is particularly fierce in the southeastern area of the city," a Western NGO official told AFP on condition of anonymity.
"There are still a few people on the streets but far less than usual."
Taliban spokesman Zabihullah Mujahid claimed responsibility for the attacks, adding their fighters had overrun several checkpoints and killed 12 Afghan soldiers. The toll could not be verified.
The militants were also laying siege to all the city's checkpoints, police stations, and the governor's headquarters, Mujahid added.
The Taliban have been waging a bloody insurgency since a US-led invasion ousted them from power in late 2001, and have stepped up attacks during a summer offensive launched in late April against the Western-backed government in Kabul.
On Sunday 13 people were killed and 33 wounded at a volleyball match in the eastern province of Paktika, while Islamic State fighters launched coordinated attacks on police checkpoints in the eastern province of Nangarhar.
The Taliban denied being behind the attack in Paktika, a volatile frontier region considered a stronghold of their allies the Haqqani network.
The rival Islamic State group meanwhile has been been making inroads in Afghanistan over the past year, with its well-planned strikes on Sunday seen as a sign of its rising influence.
Retired General Atiqullah Amarkhil, a security analyst, said IS had chosen its targets in the Achin district because they were trying to gain control of an eastern highway connecting Afghanistan to Pakistan.
"Secondly, IS has chosen Achin and other Nangarhar province districts in order to gain control of the drug trade. IS needs such revenue streams in order to fight," he added.
Afghanistan's NATO-trained police and army have been fighting the Islamist militants this year without the front-line help of foreign forces, which ended their combat mission in December 2014.
A residual force of around 13,000 remains for training and counter-terrorism operations.
Peace overtures by the government of President Ashraf Ghani over summer ended in failure, as civilian casualties soared to a record high in the first half of 2015 according to a UN report.
It said 1,592 civilians were killed, a six percent fall over last year, while the number of injured jumped four percent to 3,329.