The Taliban are once again close to capturing Sangin, a crucial district in Helmand where more than 100 British soldiers lost their lives.
The insurgents were repulsed in December by Afghan army and police reinforcements but have launched a string of ferocious attacks in recent days.
Local commanders say most of the district has fallen and the government is left in control of only a few miles around Sangin City.
Although officials insist the district remains secure, a commander told the BBC said the Taliban had overrun a base three days ago, killing eight soldiers and taking nine more prisoner.
They managed to seize an armoured vehicle and all the base's weapons and ammunition.
“Two other camps are also under threat, if they don't get the support needed, God forbid, they will have the same fate,” he said.
The opium-rich province of Helmand has seen some of the fiercest fighting of the 14-year conflict.
Tony Blair sent 3,300 troops there in early 2006, as part of a plan to cut off the Taliban's main source of income and close an international heroin supply routes.
By the time the UK handed control of Sangin to American forces in 2010, the district had claimed 106 British lives – a quarter of all British casualties.
For the past year, Afghan forces have been struggling to stop the Taliban gaining ground.
The the US and Nato ended their combat missions at the end of 2014.
Meanwhile, Afghanistan announced it expected to hold direct talks with the Taliban by the end of this month.
Ahmad Shakib Mostaghani, foreign ministry spokesman, said Afghanistan, Pakistan, China and the United States agreed on steps toward peace talks at a meeting in Islamabad at the weekend. He said the government hoped to "put an end to the futile violence which is imposed on our people”.
The last direct talks between Kabul and the Taliban broke down after just one session last summer when Kabul announced that the Taliban's reclusive, long-time leader Mullah Mohammad Omar died two years earlier.