CAIRO -- Libya’s second-largest city, Benghazi, was reported tense Thursday ahead of two major rallies called for Friday, one to show support for the United States and its slain ambassador, who died last week when gunmen stormed the U.S. consulate compound, and the other by the Ansar al Shariah militia suspected of involvement in the attack.

Ansar al Shariah called its rally for the same time and the same place as a group of moderate Libyans who call themselves “Save Benghazi.”

“Ansar al Shariah has done this deliberately,” said Bilal Bettamir, one of the organizers of the Save Benghazi rally, which in addition to marking the passing of U.S. Ambassador Christopher Stevens is intended to call for freedom of expression and religious moderation. “We have been planning our march for the past week, and they made their decision yesterday. They knew all about it.”

The stark differences between the two sides were evident in an interview with the head of Ansar al Shariah aired Thursday by the United States’ National Public Radio network. Mohammed Zahawi showed nothing but contempt for Western ideals.

"As for those bankrupt calls for Western democracy, liberalism and secularism, what did democracy give to the West?” he said, according to an account of the interview posted on the NPR website. “Social collapse, moral collapse, economic collapse?"

Ansar al Shariah is by far the dominant armed group in eastern Libya, where the national government in Tripoli has so far been unable to establish a security presence. The group has denied that it is responsible for the assault on the consulate, but witnesses have told McClatchy that the 100 to 125 gunmen who stormed the consulate compound with grenades, rockets and automatic weapons fire were carrying the Ansar al Shariah flag.

"The liberals and secularists were all raised in the West,” Zahawi told NPR. “They were raised in openness, nakedness and decay. They know that in an Islamic state, they can’t get to their vices. That’s why they are waging a war against Islam."

In Washington, Secretary of State Hillary Clinton announced the formation of a panel to investigate the deaths of Stevens and the three other Americans: computer expert Sean Smith and two former Navy SEALs, Greg Doherty and Tyrone Woods, who were working as security contractors at the consulate.

The panel – the formation of which is usually pro forma in such cases – is to be chaired by Thomas Pickering, a retired diplomat who served in the third highest post at the State Department and as a U.S. ambassador to Russia, India, Israel and the United Nations.

Clinton made the announcement before going to Capitol Hill to provide closed-door briefings to the Senate and the House of Representatives on the consulate attack. She was joined by Director of National Intelligence James Clapper and other senior officials.

A House subcommittee chairman, meanwhile, informed Clinton that his panel would conduct its own investigation, and he cited the differences in the U.S. and Libyan versions of what happened.

"The universe of known facts . . . remains small and confusion has overshadowed certainty in this matter," Rep. Jason Chaffetz, R-Utah, chairman of the House Subcommittee on National Security, Homeland Defense and Foreign operations, wrote to Clinton in a letter. "The American people have a right to know precisely what happened."