The attack occurred around 1:30 p.m. local time at Camp Antonik in Washer District in Helmand.
"Coalition security forces on the base killed the soldier to end the attack," Capt. Bill Salvin, spokesman for U.S. Forces in Afghanistan, told Fox News. "The U.S. soldiers are receiving medical treatment at this time and we will release more information when available."
The severity of the soldiers wounds was not immediately clear. Salvin declined to offer more details.
There are roughly 8,400 U.S. troops on the ground in Afghanistan -- more than in Iraq and Syria combined.
Additionally, the Pentagon is weighing a decision to send more U.S. forces to Afghanistan. The top U.S. commander in the country, Gen. John Nicholson, told Congress earlier this year he needed more U.S. and allied soldiers to help train the Afghan army.
A detachment of U.S. Marines is scheduled to replace the Army unit in Helmand Province in the coming weeks. Hundreds of Marines were killed fighting the Taliban in Helmand at the height of the Afghan war.
Since October, 12 Americans have been killed in Afghanistan and five Americans are currently being held hostage there.
Obama-era force management levels, known more broadly as "troop caps," have strictly controlled the number of U.S. soldiers on the ground in Afghanistan (and Iraq and Syria, too).
During a recent visit to Ft. Campbell, home of the famed 101st Airborne Division, Apache gunship pilots told Fox News about the recent deployment of 101's aviation brigade to Afghanistan -- only the helicopters and pilots deployed. The mechanics were left at home because of the troop caps.
As a result, expensive contractors were paid tens of millions of dollars to fix the helicopters overseas.
|© FoxNews. More troops are needed because many Afghan troops were killed by the Taliban; Jennifer Griffin has the details for 'Special Report'|
Three US soldiers wounded in Afghan 'insider attack'
Three American troops were wounded Sunday when an Afghan soldier opened fire in southern Helmand province, officials said, in the first known "insider attack" on international forces this year.
No insurgent group has so far claimed responsibility for the attack in Camp Antonik in Washer district, which highlights long-simmering tensions between Afghan and foreign forces.
"Three US soldiers were wounded this afternoon when an Afghan soldier opened fire on them at a base in Helmand province. Coalition security forces on the base killed the soldier to end the attack," a spokesman for US forces in Afghanistan told AFP.
"The US soldiers are receiving medical treatment at this time and we will release more information when available."
An Afghan soldier was also killed in the shootout, provincial spokesman Omar Zwak told AFP.
The Pentagon has said it would deploy some 300 US Marines this spring to Helmand province, where American forces engaged in heated combat until they pulled out in 2014.
The Marines will head to the poppy-growing province this spring to assist a NATO-led mission to train Afghan forces, in the latest sign that foreign forces are increasingly being drawn back into the worsening conflict.
So-called insider attacks -- when Afghan soldiers and police turn their guns on their colleagues or on international troops -- have been a major problem during the more than 15-year-long war.
In May last year, gunmen wearing Afghan military uniforms shot dead two Romanian soldiers in neighbouring Kandahar province.
Western officials say that most such attacks stem from personal grudges and cultural misunderstandings rather than insurgent plots.
The killings have bred fierce mistrust between local and foreign forces even as the rate of such incidents has dropped in recent years.
The Afghan military, which has been built from scratch since the fall of the Taliban regime in 2001, has also struggled with insider attacks, high casualty rates and mass desertions.
Three US troops wounded after Afghan soldier opens fire
An Afghan soldier opened fire on Sunday inside a base in the southern Helmand province, wounding three US soldiers before being shot dead, an Afghan official said.
Colonel Mohammad Rasoul Zazai, an army spokesman, said the soldier had made a “mistake” and had not fired deliberately. A coalition-run Twitter account said an Afghan soldier shot and wounded three American soldiers, without providing further details.
Several US troops have been killed in Afghanistan in recent years in so-called insider attacks carried out by Afghan police or soldiers. In October, an Afghan man in a military uniform shot dead a US soldier and an American civilian contractor inside a military base in Kabul before being killed.
Most foreign combat troops withdrew from Afghanistan at the end of 2014, 13 years after they ousted the Taliban from power, but about 13,000 Nato-led soldiers remain to help advise and train Afghan forces fighting a revived Taliban insurgency.
Last May two Romanian soldiers were killed and a third wounded after two members of a local Afghan police unit they were training shot them.
Camp Shorab in Helmand, previously known as Camp Bastion, is a major former US and British base now run by the Afghan army.
Helmand has been one of the most fiercely contested regions of the country, with nearly 1,000 coalition troops killed there since the US-led military intervention in 2001.
The US said in January that about 300 marines would be sent to Helmand to assist Afghan forces battling the Islamist insurgents in intelligence and logistics matters.
Elsewhere in Afghanistan, Taliban insurgents attacked a district headquarters in the Kandahar province using a suicide car bomb, said Samim Khpolwak, a spokesman for the governor. He declined to say how many people were killed or wounded.
A security official, who spoke on condition of anonymity because he was not authorized to release information, said six police were killed and five others were wounded in the assault, which was claimed by the Taliban.
In the southern Zabul province, an army operation killed 13 Taliban and wounded 11 others, said General Sadiqullah Saberi. He said two Afghan soldiers were killed and three others were wounded by a roadside bomb during the operation.
Two Taliban commanders were killed in an apparent US drone strike in the Barmal district of the eastern Paktika province, said Mohammad Rahman Ayaz, spokesman for the provincial governor.
Another 10 insurgents were killed in a separate drone strike in the Dand-e Patan district of neighboring Paktia province, said Governor Zelmai Wessa.