Three U.S. Army soldiers were shot and wounded Sunday when an Afghan Army soldier opened fire on them inside a base in southern Afghanistan's volatile Helmand Province, officials told Fox News.

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.