Tunisian officials said today a 28-year-old Tunisian linked to the deadly attack on the U.S. Consulate in Benghazi, Libya, this past Sept. 11 is in custody, as controversy grew over whether the U.S. knew if the assault was a deliberate act of terrorism.

Tunisian Interior Ministry spokesman Tarrouch Khaled said Ali Harzi was in custody in Tunis.

Harzi's lawyer Ouled Ali Anwar said his client was told by a judge Tuesday that he has been charged with "membership of a terrorist organization in a time of peace in another country."

A person who saw Harzi's court dossier told The Associated Press that prosecutors are linking him to the Sept. 11 attacks on the U.S. Consulate in Benghazi that left Ambassador J. Christopher Stevens and three other Americans dead. He said Harzi is one of two Tunisians arrested Oct. 3 in Turkey when they tried to enter the country with false passports.

The person spoke on the condition of anonymity because he was not authorized to release the information. Harzi's alleged role in the attacks is not clear.

Anwar denied there was any evidence that Ali "is implicated in the Benghazi attacks." He added his client was not using a fake passport, saying he was used as a "scapegoat to satisfy the Americans

In Washington, the State Department had no comment. Earlier this month, Defence Secretary Leon Panetta said the U.S. has been looking into the arrests of two Tunisian men being detained in Turkey reportedly in connection with the attack.

Emails notified U.S. officials of claim by militants

Emails obtained by several news organizations indicate U.S. officials were notified two hours after a fatal attack on its consulate in Benghazi that an Islamic militant group claimed credit.

The emails regarding the attack were sent from a U.S. State Department address to various government agencies, including the White House and the Federal Bureau of Investigation (FBI), reports say.

Christopher Stevens was the U.S. ambassador to Libya. He was killed along with three embassy staff on Sept. 11. (Esam Al-Fetori/Reuters)

One email, which was sent from the U.S. State Department Operations Centre, had the subject line: "Ansar al-Sharia Claims Responsibility for Benghazi Attack."

"Embassy Tripoli reports the group claimed responsibility on Facebook and Twitter and has called for an attack on Embassy Tripoli," reads the email sent two hours after the assault, CNN reports.

Serious questions have been building for weeks about the deadly attack on the consulate, and what U.S. officials knew about its nature.

It's become a key issue in the U.S. presidential race ahead of the vote on Nov. 6. President Barack Obama and Republican presidential nominee Mitt Romney sparring in recent debates over U.S. officials' response in the assault's aftermath.

Romney has accused the White House of misleading Americans about the nature of the attack.

Claim 'not in and of itself evidence': Clinton

Secretary of State Hillary Rodham Clinton said Wednesday that the State Department emails do not tell the whole story.

Clinton told reporters that the claim of responsibility noted by department officials was posted on Facebook and "is not in and of itself evidence." She cautioned against "cherry picking one story here or one document there" and said it is critical to look at the totality of information before coming to any conclusions.

News organizations obtained the unclassified email and two related emails from government officials who requested anonymity because they were not authorized to speak about them publicly, according to the Associated Press.

The U.S. Consulate was stormed and set on fire. (Esam Al-Fetori/Reuters)

The newly released emails shed light on U.S. knowledge of the attack as it unfolded.

The first email, sent at 4:05 p.m. ET, said that the diplomatic mission in Benghazi was "under attack".

"Embassy Tripoli reports approximately 20 armed people fired shots; explosions have been heard as well."

Stevens and four other personnel were in the compound's "safe haven", it added.

At 4:54 p.m. ET, an email update said that the firing at the Benghazi Consulate had stopped and the compound was cleared, according to the U.S. Embassy in Tripoli.

The third email reporting the claim of responsibility by Ansar al-Sharia was sent at 6:07 p.m.

'There were emails about all sorts of information'

White House press secretary Jay Carney said the emails represented just one piece of information the administration was receiving at the time.

Carney, travelling with President Obama Wednesday on Air Force One, said the emails were unclassified and referred to assertions made on a social media site.

"There were emails about all sorts of information that was becoming available in the aftermath of the attack," Carney said.

"The whole point of an intelligence community and what they do is to assess strands of information and make judgments about what happened and who is responsible."

Ansar al-Sharia bragged to members of al-Qaeda in the Islamic Maghreb that it was responsible for the attack, according to recordings of phone calls intercepted by U.S. intelligence. But the group has publicly denied having anything to do with the attack.