The Taliban have captured another three provincial capitals in southern Afghanistan, including in Helmand, the scene of some of the heaviest fighting in the past two decades, as the insurgents press a lightning offensive that is gradually encircling the capital, Kabul.

The loss of Helmand’s provincial capital comes after years of toil and blood spilled by American, British, and allied NATO forces. Hundreds of foreign troops were killed there over the course of the nearly two-decade war.

The insurgents have taken more than a dozen provincial capitals in recent days and now control more than two-thirds of the country just weeks before the U.S. plans to withdraw its last troops.

Attaullah Afghan, the head of the provincial council in Helmand, says that the Taliban captured the provincial capital of Lashkar Gah following heavy fighting and raised their white flag over governmental installations. He says that three national army bases outside of Lashkar Gah remain under the control of the government.

Atta Jan Haqbayan, the provincial council chief in Zabul province, said the local capital of Qalat fell to the Taliban and that officials are in a nearby army camp preparing to leave.

Two lawmakers from Afghanistan’s southern Uruzgan province said local officials have surrendered the provincial capital, Tirin Kot, to the rapidly advancing Taliban.  The governor is en route to the airport to depart for Kabul.

The latest advances came hours after the insurgents captured the country’s second and third largest cities in a lightning advance. The seizures of Kandahar and Herat mark the biggest prizes yet for the Taliban.

While Kabul isn’t directly under threat yet, the losses and the battles elsewhere further tighten the grip of a resurgent Taliban, who are estimated to now hold over two-thirds of the country and continue to press their offensive.

With security rapidly deteriorating, the United States planned to send in 3,000 troops to help evacuate some personnel from the U.S. Embassy in Kabul. Separately, Britain said about 600 troops would be deployed on a short-term basis to support British nationals leaving the country, and Canada is sending special forces to help evacuate its embassy.

Thousands of Afghans have fled their homes amid fears the Taliban will again impose a brutal, repressive government, all but eliminating women’s rights and conducting public executions.

Peace talks in Qatar remain stalled, though diplomats are still meeting, as the U.S., European and Asian nations warned that any government established by force would be rejected.