The SAS and US special forces troops have joined the Afghan Army to battle Taliban fighters in Sangin, a city in the north of country's notorious Helmand Province, it has been reported. A Ministry of Defence (MoD) spokesman told the IBTimes UK that a small number of UK military personnel had been deployed to the opium-rich region "in an advisory role".

"There are around 450 (British) troops in Afghanistan overall who are mentoring and supporting the Afghan forces there," he said. "They are in the main, army (personnel)." But there are only a small number in Helmand itself as part of Nato's resolute support mission, he added.

He adding that the MoD had no comment on reports that British troops were part of 300 strong contingent of coalition troops that arrived in the region on Christmas Eve, saying, "We don't talk or give any guidance on special forces."

But a number of reports in the UK and Afghanistan have suggested that the SAS have been doing more than offer advice to the country's forces in the region that has traditionally been a Taliban heartland.

Afghan journalist Bilal Sarwary tweeted on Christmas Day that his country's Special Forces had been accompanied by SAS troops on night raids in the region.

The infamous special forces unit had provided help with intelligence, said Sarwary, who has written for the New York Times and the Independent, among other publications.

This report followed a 22 December report in The Times newspaper, which said that up to 60 US special forces, backed by at least one British SAS unit of about 30 troopers, joined Afghan troops in the battle to save the town.

The following day, Colonel Michael T Lawhorn told US broadcaster CNN there were two US-led airstrikes in Sangin against Taliban fighters in the field who posed a threat to Afghan forces.

Meanwhile, The Mail on Sunday printed a picture on 27 December purporting to show SAS soldiers in the region, although the paper said it had not been able to verify their nationality and they could have come from another country.

Importance of Sangin

December marks one year since Nato handed over security operations to the Afghans. Before that, British and US forces struggled for years to hold on to Sangin, a fertile area that is a juncture to one of the biggest poppy growing regions in the world.

UK troops handed control over to the Americans in 2010. More than 100 of the 450 British troops killed during the campaign in Afghanistan died in Sangin.

Sangin "was significant because of the routes it controlled and it was a very significant part of the resourcing of the political economy of Helmand, because it is a major center of drugs processing and drugs shipping," Stuart Gordon, a Helmand expert at the Chatham House thinktank told the Press Association last week.

If the Taliban took control of Sangin, they would control supply routes to the districts and gain valuable influence over neighbouring provinces, he added.

The fighting in the region has been so fierce that the deputy governor of Helmand province, Mohammad Jan Rasolyaar, took the unusual step of posting an open letter to Afghanistan's President Ashraf Ghani on Facebook.

"Your Excellency, Facebook is not the right forum for speaking with you, but as my voice hasn't been heard by you I don't know what else to do," he wrote. "Please save Helmand from tragedy. Ignore those liars who are telling you that Helmand is secure."