An Islamist Web site recently posted an item titled "How to Join Al Qaeda," calling on Muslims to regard jihad as a personal duty and to buy weapons, brainstorm and plot plans to kill Americans.

"Assassinating the ambassador takes no more than a gun and a bullet," according to the alleged posting.

A jihad cell should have no more than five members — "all absolutely trustworthy" — with a commander who is "Osama bin Laden to the cell members," according to the posting.

After obtaining funding, members of a cell should "buy weapons, make plans, brainstorm, plot your plans, monitor your enemy's important objectives, and study its moves," according to the posting. "Set a goal; for example, assassinating the American ambassador — is it so difficult? Is it difficult for something who has already crushed America in her own home?"

The members must be secret, perform intelligence tasks, collect information, raise funds, recruit other members and assist in operations.

"Those who act in the open must perform the primary military operations, such as assassinations, firing at enemy facilities, etc.," according to the post.

The Middle East Media Research Institute, a group based in Washington, D.C., that monitors about 90 of these types of Web sites, translated the posting. The Web site started in Egypt, then went inactive and appeared again under a different name. The Web site passed through Site Genie, an American service provider in Rochester, Minn.

Click here to read the report from the Middle East Media Research Institute.

The Minnesota Joint Terrorist Task Force is investigating the alleged posting, said Paul McCabe, a spokesman for the FBI in Minneapolis.

FOX News' Jennifer Griffin contributed to this report.