(AP) John Walker Lindh, the Californian who took up arms for the Taliban and was captured by invading U.S. forces in Afghanistan in 2001, got out of prison Thursday after more than 17 years, released under tight restrictions that reflected government fears he still harbors radical views.

Lindh, 38, left a federal penitentiary in Terre Haute, Indiana, after getting time off for good behavior from the 20-year sentence he received upon pleading guilty to providing support to the Taliban.

It was not immediately clear where the man known as the "American Taliban" will live or what he will do.

In a Fox interview, Secretary of State Mike Pompeo condemned his early release as "unexplainable and unconscionable" and called for a review of prison system policies.

Lindh's release was also opposed by the family of CIA officer Mike Spann, who was killed during an uprising of Taliban prisoners shortly after interrogating Lindh in Afghanistan.

Under restrictions imposed by a federal judge in Alexandria, Virginia, Lindh's internet devices must have monitoring software; his online communications must be conducted in English; he must undergo mental health counseling; he is forbidden to possess or view extremist material; and he cannot hold a passport or leave the U.S.

Probation officers never explained why they sought the restrictions, but it is clear authorities retain misgivings about Lindh. In 2017, Foreign Policy magazine cited a National Counterterrorism Center report that Lindh "continued to advocate for global jihad and to write and translate violent extremist texts."

On Wednesday, NBC reported that Lindh, in a letter to a producer from Los Angeles-based affiliate KNBC, wrote in 2015 that the Islamic State group is "doing a spectacular job" and "is clearly very sincere and serious about fulfilling the long-neglected religious obligation to establish a caliphate through armed struggle."

Lindh converted to Islam as a teenager after seeing the movie "Malcolm X," went overseas to study Arabic and the Quran and eventually made his way to Pakistan and Afghanistan and joined the Taliban. He met Osama bin Laden and was with the Taliban on Sept. 11, 2001, when al-Qaida terrorists attacked the World Trade Center and the Pentagon.

Lindh was captured in a battle with U.S.-allied Northern Alliance fighters in late 2001. He was present when a group of Taliban prisoners launched an attack that killed Spann.

Spann's daughter Alison Spann, now a journalist in Alabama, posted a letter on her Twitter account that she said she had sent to President Donald Trump. In it, she called Lindh's early release "a slap in the face" to everyone killed on 9/11 and in the war on terror since then, along with "the millions of Muslims worldwide who don't support radical extremists."

Lindh was initially charged with conspiring to kill Spann. He denied any role in Spann's death but admitted carrying an assault rifle and two grenades.

Republican Alabama Sen. Richard Shelby and Democratic New Hampshire Sen. Maggie Hassan also expressed concern about Lindh's release in a letter last week to the Bureau of Prisons.

"We must consider the security and safety implications for our citizens and communities who will receive individuals like John Walker Lindh who continue to openly call for extremist violence," they wrote.

The bureau defended itself Thursday in a statement that said Lindh's release followed federal laws and guidelines. It said it works closely with outside agencies "to reduce the risk terrorist offenders pose inside and outside of prisons," and added that no radicalized inmate has returned to federal prison on terrorism-related charges.