Thousands of fighters opposed to the Taliban can return "anytime" in the Panjshir Valley, said the uncle of a commander who led fierce battles against the Islamists, appealing on Tuesday for international support for their cause.

Ahmad Wali Massoud was speaking in Switzerland, one day after the Taliban claimed total control over Afghanistan, declaring that they had won the battle against resistance forces in the mountainous Panjshir Valley, northeast of Kabul.

"We still have thousands of fighters in the valley, and any time they can come back and you will be witnessing that one," Massoud told a symposium in Geneva.

"Yes, we have been wounded and we have been really wounded, but we have not died, we are still alive," he added.

Massoud is brother of the late Ahmad Shah Massoud, the legendary anti-Soviet and anti-Taliban commander assassinated by Al-Qaeda days before the September 11, 2001 attacks on the United States.

Shah Massoud's son, Ahmad Massoud, led resistance to the Taliban in the Panjshir Valley.

On Monday, the Taliban said they had won that battle in what was the last remaining holdout against their rule. They released a video of their flag being raised over the governor's house in Panjshir.

"Panjshir is not only resistance, (it) is a cause, an international cause," Massoud told the symposium.

"We are resisting for our own right, for the freedom, for democracy, for the human rights..."

"Probably this is the last opportunity that we can see to really fight terrorism inside Afghanistan," he added.

"That's why we should not lose the resistance."

The National Resistance Front (NRF) in Panjshir -- made up of anti-Taliban militia and former Afghan security forces -- on Sunday acknowledged suffering major battlefield losses and called for a ceasefire.

But on Monday the group said in a tweet that its fighters were still present in "strategic positions" in the valley.