(Recasts with details, State Department comments)

By Rafiq Sherzad

JALALABAD, Afghanistan, April 8 (Reuters) - An Afghan man dressed in the uniform of local security forces opened fire on U.S. soldiers in eastern Afghanistan on Wednesday, killing one American and wounding several more before the shooter himself was killed, a U.S. official said.

Many details surrounding the incident were still unclear. The Pentagon and U.S. State Department only confirmed an exchange of gunfire between U.S. and Afghan forces, saying an investigation was ongoing.

"I can confirm that one American soldier was killed today," Colonel Steve Warren, a Pentagon spokesman, told reporters.

Asked whether this was an insider attack by an Afghan soldier turning his weapon against NATO forces, Warren said: "It's a little early to tell. Indications are leaning that way."

"But we need to let a little more information come out first," Warren added.

Two Afghan soldiers were also injured in the shootout, but it was unclear who had fired first, Afghan police said.

A U.S. official, speaking on condition of anonymity, said shooting was initiated by an unidentified Afghan man dressed in the uniform of Afghan security forces. He was killed in the ensuing return fire from American troops.

A second U.S. official estimated that around six Americans were wounded.

The U.S. State Department acknowledged only that an exchange of gunfire took place about an hour after State Department officials held a meeting with the provincial governor in Jalalabad. They had left the site before the shooting began, officials said.

"I have seen nothing to indicate they were targeted though, and I know the investigation is ongoing," said State Department spokeswoman Marie Harf.

The frequency of "insider attacks" in Afghanistan has fallen sharply this year as most foreign forces withdrew from the country in 2014.

A small contingent of around 12,000 NATO troops remains in Afghanistan to train Afghan forces after the combat mission officially ended last year.

Wednesday's incident was the first since January, when three U.S. military contractors were killed by an Afghan soldier in the capital Kabul.

In the final years of the war, dozens of incidents seriously eroded trust between Afghan forces and their international allies, forcing the coalition to scale back interaction with government troops.

The Taliban have sometimes claimed that insider attacks reflect their ability to infiltrate the enemy, but Afghan and coalition forces say incidents more often arise over misunderstandings or arguments between troops. (Reporting Rafiq Sherzad in Jalalabad, Mirwais Harooni and Jessica Donati in Kabul, Phil Stewart and Emily Stephenson in Washington, writing by Jessica Donati and Phil Stewart; editing by Simon Cameron-Moore, G Crosse Andrew Hay)

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