The Taliban captured a sixth provincial Afghan capital on Monday, a lawmaker said, after ousting Afghan security forces from border towns and trade routes as US-led foreign forces pull out.
The group has stepped up its campaign to defeat the government as foreign forces withdraw after 20 years of war.
On Monday, they took Aybak, capital of the northern province of Samangan.
"Right now the Taliban are fighting with Afghan forces to capture the police headquarters and compound of the provincial governor," said Ziauddin Zia, a lawmaker in Aybak.
"Several parts of the capital have fallen to the Taliban."
The insurgents took three provincial capitals over the weekend - Zaranj, the capital of the southern province of Nimroz, Sar-e-Pul, the capital of the northern province of the same name, and Taloqan, the capital of northeastern Takhar province.
They had already taken the northern provincial capital of Kunduz and Lashkar Gah, capital of southwestern Helmand province.
The Taliban gains have sparked recriminations over the withdrawal of foreign forces.
British Defence Secretary Ben Wallace told the Daily Mail that the accord struck last year between the United States and the Taliban was a "rotten deal".
Wallace said his government had asked some NATO allies to keep their troops in Afghanistan once the US troops departed, but failed to garner enough support.
"Some said they were keen, but their parliaments weren’t. It became apparent pretty quickly that without the United States as the framework nation it had been, these options were closed off," Wallace said.
Germany's defence minister rejected calls for its soldiers to return to Afghanistan after Taliban fighters took Kunduz where German troops were deployed for a decade.
Afghan commandoes had launched a counter-attack to try to beat back the Taliban who overran Kunduz, with residents fleeing the conflict describing the almost constant sound of gunfire and explosions.
A Taliban spokesman warned the United States on Sunday against intervening following US airstrikes to support beleaguered Afghan government forces.
The United States has vowed to pull out most troops by the end of the month, ending its longest war.
In the West, near the border with Iran, security officials said heavy fighting was under way on the outskirts of Herat. Arif Jalali, head of Herat Zonal Hospital, said 36 people had been killed and 220 wounded over the past 11 days.
More than half of the wounded were civilians, he said, and women and children were among the dead.
UNICEF in a statement on Monday said 20 children were killed and 130 children had been injured in southern Kandahar province in the last 72 hours.
"The atrocities grow higher by the day," said Hervé Ludovic De Lys, UNICEF's representative in Afghanistan.