LASHKAR GAH, Afghanistan (Reuters) - Afghan security forces backed by U.S. air strikes have beaten back Taliban attacks on a vulnerable southern district, government officials said on Wednesday, after a relative lull in fighting over the month of Ramadan.

In recent days, Taliban forces launched attacks on the Sangin district center, an outpost in Helmand province repeatedly threatened by militants over the past year.

"Taliban insurgents attacked our security outposts on Sunday but faced fierce resistance from Afghan forces and were pushed back," said Omar Zwak, a spokesman for the provincial governor.

Dozens of militants were killed in the fighting, including the Taliban's shadow district governor in Sangin, Mawlawi Agha, Zwak said.

A Taliban spokesman, Qari Yousef Ahmad, said his fighters had captured the district center but Afghan and U.S. military officials rejected that.

U.S. warplanes had conducted at least two air strikes in the 24 hours up to Wednesday afternoon in support of Afghan troops, but officials declined to provide additional details on the fighting.

U.S. Defense Secretary Ash Carter said on a visit to Afghanistan last week that U.S. forces would have greater freedom to strike at the Taliban under broad new powers approved last month by President Barack Obama.

Sangin is in a strategic area for the lucrative opium trade, which provides funding for the Taliban, as well as other strongmen.

The district center is a small, government-controlled enclave in an area otherwise largely dominated by the Taliban, who have increased their stranglehold on the district over the past year.

Fighting intensified in Afghanistan after the Taliban announced the start of their annual warm-season offensive in April, but it tailed off during the Muslim fasting month of Ramadan, which ended early this month.

(Reporting by Mohammed Stanekzai; Writing by Josh Smith; Editing by Robert Birsel)