A motorcycle-riding Taliban suicide bomber killed six US soldiers near Kabul on Monday, in a brazen attack as the resurgent militant group battled to seize a key southern district in Afghanistan’s opium-growing heartland, reported AFP.

The bombing during a joint patrol with Afghan forces near Bagram, the largest US military base in Afghanistan, marks one of the deadliest attacks on foreign troops in the country this year.

The Taliban claimed responsibility for the attack, which marks a worsening security situation a year after NATO formally ended its combat operations in Afghanistan.

Three Afghan police officers also were wounded in the blast, an Afghan official said.

According to WaPo, “We’re deeply saddened by this loss,” said Brig. Gen. Wilson A. Shoffner, the top U.S. military spokesman in Afghanistan. Gen. John Campbell, the U.S. commander in Afghanistan, and the rest of the military coalition said that “our heartfelt sympathies go out to the families and friends of those affected in this tragic incident, especially during this holiday season,” Shoffner added.

In emailed statements and tweets on Monday, the Taliban claimed responsibility for the suicide attack on American soldiers near Bagram and said its forces had successfully overtaken the strategic Sangin district of Helmand province in the south.

A statement from the insurgents said a “self-sacrificing attacker” named Zahidullah, riding a motorbike, targeted American soldiers patrolling in Bagram. The statement also said that 19 American “occupiers” were killed and “a huge number” wounded. The Taliban often exaggerates enemy casualty numbers.

Local residents reported crippling food shortages in the district, long seen as a hornet’s nest of insurgent activity after the Taliban began storming government buildings on Sunday.

“The Taliban have captured the police headquarters, the governor’s office, as well as the intelligence agency building in Sangin,” deputy Helmand governor Mohammad Jan Rasoolyar, told AFP.

“Fighting is escalating in the district,” he said, claiming the number of soldiers killed in clashes is “unbelievably high”.

Rasoolyar’s comments come a day after he posted a desperate plea on Facebook to President Ashraf Ghani, warning the entire province was at risk of falling to the Taliban.

The government in Kabul said reinforcements had been dispatched to Sangin, while denying claims of large casualties and rejecting that the district was at risk of being captured.