The UK says it has sent military personnel to the southern Afghanistan province of Helmand following reports that the district capital Sangin is on the verge of falling to Taliban forces.
Helmand's governor said on Monday Afghan police were holding out against Taliban fighters who had surrounded their compound and the district governor's building in Sangin but roads into the town were completely controlled by the Taliban.
He warned the situation risked slipping entirely out of control.
Britain, which ended combat operations in Afghanistan last year but has about 450 troops there to mentor and support the Afghan army and security forces, said a small number of personnel had been deployed to Helmand in an advisory role.
London's Times newspaper reported on Tuesday that a unit of about 30 soldiers from Britain's elite Special Air Service (SAS) and up to 60 US special forces had been sent to bolster the Afghan forces to defend the town, but the Ministry of Defence (MoD) said the team would not be engaged in fighting.
"These personnel are part of a larger NATO team, which is providing advice to the Afghan National Army," an MoD spokeswoman said. "They are not deployed in a combat role and will not deploy outside the camp."
Helmand, a major centre of opium cultivation and a traditional Taliban heartland, has been the scene of fierce fighting for months as the insurgents ramp up attacks.
British and American forces struggled for years to control the volatile province, and many of the more than 450 British servicemen and women killed in Afghanistan lost their lives fighting there.
Last week, the Pentagon warned of deteriorating security in Afghanistan and assessed the performance of Afghan security forces as "uneven and mixed".
Six American troops were killed in Afghanistan on Monday when a suicide bomber on a motorbike struck their patrol near Bagram air base.
