The U.S. launched air strikes to bolster Afghan forces scrambling Thursday to beat back Taliban fighters who seized large swathes of a key district, following the first British deployment to the volatile region in 14 months.

The Taliban fighters claim to have captured nearly the entire district of Sangin after storming its frontlines on Sunday, tightening their grip on the southern Helmand province.

The U.S. army conducted air strikes on Wednesday to back up Afghan forces mobilizing reinforcements to relieve dozens of security forces holed up in the district center.

"U.S. forces conducted two strikes in Sangin," a NATO spokesman said in a brief statement.

Taliban spokesman Zabiullah Mujahid said fighters had overrun the whole of Sangin, pinning down Afghan forces in a military base where trapped soldiers reported dire conditions.

The war in Helmand follows a string of military victories for the Taliban after NATO formally ended its combat operations last year.

All but two of Helmand's 14 districts are effectively controlled or heavily contested by the Taliban, who also recently came close to overrunning the provincial capital Lashkar Gah.

Britain on Tuesday said a small contingent of its troops had arrived in Camp Shorabak, the largest British base in Afghanistan, before it was handed over to Afghan forces last year.

The deployment, in addition to a recent arrival of U.S. special forces in the region, is the first since British troops ended their combat mission in Helmand in October 2014.

The Taliban on Wednesday slammed the British deployment after last year's pullout as "a sign of stupidity" and threatened to target the "newly arrived invaders".

The intervention has fuelled the perception that foreign forces are increasingly being drawn back into the conflict as NATO-trained Afghan forces struggle to rein in the Taliban.

US President Barack Obama in October announced that thousands of U.S. troops would remain in Afghanistan past 2016, acknowledging that Afghan forces are not ready to stand alone.

PHOTO CAPTION

Afghan National Army soldiers guard at a checkpoint on the way to the Sangin district of Helmand province, Afghanistan, Wednesday, Dec. 23, 2015.

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