Afghan troops have retreated from two districts in the southern province of Helmand, officials said Monday, a move which highlights the challenge from Taliban fighters in the opium-producing region.

"The Afghan army retreated from two army bases in Musa Qala and one base from Nawzad district" on Saturday, provincial governor Khan Rahimi told AFP, leaving no troops anywhere in those districts.

He said the soldiers had moved to other parts of Helmand such as the heavily-contested districts of Lashkar Gah and Sangin, adding: "We have no concerns regarding this step but we have plans to ensure security in other vulnerable areas."

But the decision was criticised by Abdul Majeed Akhundzada, deputy chief of the provincial council.

"Retreating from Musa Qala looks to me like ignoring the deaths of Afghan security forces and the civilians," Akhundzada said.

Helmand has seen some of the fiercest battles of the Taliban's battle against local and foreign forces that began in 2001.

The militants have intensified their campaign in the province since the NATO combat mission in the war-torn country officially ended in 2014.

Last October President Barack Obama announced that thousands of US troops would remain in Afghanistan past 2016 in what is officially a training and support role, backpedalling on previous plans to reduce the force and acknowledging that Afghan forces are not ready to stand alone.

The US has deployed several hundred troops in Helmand in recent weeks.

In August last year Taliban insurgents briefly captured the town of Musa Qala before Afghan forces backed by NATO retook it.

Last December a Taliban offensive drove Afghan forces from most of Sangin, a major poppy growing area in in the province. The onslaught raised fears that Afghan forces were too overstretched to fend off the insurgents.

"Retreating is something normal," said Moeen Faqiri, army corps commander in Helmand, adding that the areas were not heavily populated.

The retreat came days before the fourth round of talks between representatives of Afghanistan, Pakistan, China and the US to be held in Kabul.

The talks do not involve the Taliban but indicated that the insurgents may be willing to return to negotiations six months after a round of direct dialogue collapsed.