A Taliban suicide attack near the Bagram airbase in Afghanistan has left six NATO troops dead and three others injured.

A NATO spokesman said the attack happened at around 1:30 p.m local time (4:00 a.m. ET), The Guardian reports.

According to local Afghan officials, a suicide bomber riding a motorbike attacked a joint U.S.-Afghan patrol as the troops were walking through the village of Bajawryan.

A Taliban spokesman named Zabiullah Mujahed claimed the suicide bomber had been watching the troops and waiting for the right moment to strike. Although the official number of the dead is six, Mujahed claimed that 19 soldiers were killed.

Bagram is the largest international military base in Afghanistan. The base has been targeted several times this year. In September, an attack near the base killed one NATO service member.

The nationalities of the dead have not yet been announced.

Following the withdrawal of international combat forces from the country back in 2014, the Taliban insurgency quickly spread across the area.

The attack is seen as part of the Taliban’s longterm strategy to control the Helmand province. As The Associated Press reports, Muhammad Kareem Atal, the head of Helmand's provincial council, asserts that about 65 percent of Helmand is now under Taliban control.

"In every district either we are stepping back or we are handing territory over to Taliban, but still, until now, no serious action has been taken," Atal said.

Vulnerable districts across the Helmand province include Nad Ali, Kajaki, Musa Qala, Naw Zad, Gereshk and Garmser.

According to Atal, in 2015 over 2,000 members of the security forces were killed while fighting in the Helmand province.

The BBC reports that Taliban militants appear to be coming closer to overtaking the town of Sangin.

While the governor of Helmand says the authorities remain in control, the Taliban claims that the main administrative building has been abandoned.