Afghanistan's third largest city, Herat, was on the verge of falling to the Taliban on Thursday amid heavy fighting, as the militant group also established a bridgehead within 150km of Kabul.
The group claimed control over Herat and, in what would be its most significant two victories since it began cutting a swathe through the country in May, also appeared close to capturing Kandahar, a diplomatic source said.
Kandahar is Afghanistan's second largest city and the spiritual home of the Taliban, which now control about two-thirds of the country.
Kandahar and other southern and eastern areas bordering Pakistan have long been Taliban heartlands, while Herat is on the other side of the country near the border with Iran.
"As you can see, we are inside the Herat police headquarters right now," a Taliban fighter said in a video shared by the group's spokeperson, Qari Yousuf Ahmadi.
Ahmadi later said the Herat governer's office had been taken, and government forces were surrendering.
If its capture is confirmed, Herat would the tenth provincial capital - and the most significant - that the Taliban have taken in the past week.
In Kandahar, most parts of the city were under the group's control but fighting was still going on, a Taliban commander told Reuters.
Earlier on Thursday the Taliban captured Ghazni, situated on the Kandahar to Kabul road some 150 km southwest of the capital.
With phone lines down across much of the country, Reuters was unable to contact government officials to confirm which of the cities under attack remained in government hands.
US to reduce Kabul embassy staff, send troops to help
The United States will reduce staff at the embassy in Kabul to a "core diplomatic presence" and send about 3000 troops temporarily to the airport to assist as the Taliban made rapid gains.
"We've been evaluating the security situation every day to determine how best to keep those serving at the embassy safe," State Department spokesman Ned Price told reporters.
"Accordingly we are further reducing our civilian footprints in Kabul in light of the evolving security situation," Price said.
"We expect to draw down to a core diplomatic presence in Afghanistan in the coming weeks," he said, adding that the embassy was not closed.
The Pentagon said that it would send about 3000 additional US troops temporarily to Afghanistan to help secure the drawdown of personnel.
Pentagon spokesman John Kirby said the first deployment would occur in the next 24 and 48 hours to the airport in Kabul.
About 3500 additional US troops would be sent to the region to be on standby if the situation worsened, as well as 1000 personnel to help process Afghans going through a special immigration process.
The news of the embassy drawdown, first reported by Reuters, is one of the most significant signs of concern in President Joe Biden's administration about the security situation and the failure of the Afghan government to protect key cities.
It is common for the US military to send in large number of troops to evacuate personnel in combat zones.
There are thought to be about 1400 staff remaining at the US Embassy in Kabul. Officials, speaking on the condition of anonymity, said the reduction in staff was "significant."
The military mission in Afghanistan is set to end on 31 August and roughly 650 troops remain in the country to protect the airport and embassy.
UK troops sent to get Britons out as Taliban advances
The British government announced around 600 UK troops are to be sent to Afghanistan to assist British nationals to leave.
Military personnel will provide protection and help relocate UK nationals, Afghan staff and interpreters, the BBC reported.
On Friday the Foreign Office advised all British nationals to leave.
It is estimated that around 4,000 British citizens are still in the country.
The Ministry of Defence (MoD) said the additional deployment was "in light of the increasing violence and rapidly deteriorating security environment in the country".
- Reuters / BBC