Dec. 18, 2009  -- Ayman al-Zawahiri, Osama bin Laden's second-in-command, has been a regular presence on Islamic web sites for years , releasing statements and videos via al-Qaeda's propaganda arm that blast the West and urge Muslims to wage holy war. Now his wife may have joined the family business.

In what is thought to be her first public statement, Omaima Hassan published a statement on Islamic web sites Thursday that encouraged "Muslim sisters" to assist with jihad, but only in suitably feminine ways. She called supporting jihad "an obligation for all Muslims, men and women." ABC News could not independently confirm the authenticity of the statement.

In the seven-page letter, after assuring friends and family that she and her husband are safe and well, Hassan outlines the ways in which women can assist their men with jihad. Hassan suggests that women work side by side in defending Islam with their men, but underlines that the most important role for women is to support male mujahideen by caring for their children.

"Jihad is an obligation for every man and woman," wrote Hassan, "but the way of fighting is not easy for women."

"Our main role -- that I ask God to accept from us -- is to preserve the mujahideen in their sons, and homes, and their confidentiality, and to help them raise/develop their children in the best way."

But Hassan also suggests that women can become suicide bombers, which she refers to as "martyrdom missions."

Hassan also urges women to wear hijabs, or head coverings, and to ignore Western media. Zawahiri, an Egyptian-born doctor, is a polygamist who has had at least four wives, two of them widows. Fundamentalist Islamic doctrine allows men to have up to four wives at one time.

Zawahiri's first wife, Azza, who bore him six children, was killed in a U.S. airstrike in Kandahar, Afghanistan in 2001. "My favorite wife's chest was crushed by a concrete ceiling," Zawahiri later wrote.

In 2008, Zawahiri sparked controversy when he said in a two-hour recorded interview posted on a web site that Al Qaeda did not have women members, and that the role of women in jihad was limited to taking care of the children of fighters and maintaining their homes.

Earlier this week, Zawahiri released his own statement, in which he blasted Egyptian and Palestinian leaders and expressed his support for Omar Abdel Rahman, Ramzi Yousef and Khalid Sheikh Muhammad, who are all in U.S. custody.

On Thursday, Al Qaeda's propaganda arm also released a 65-page book by Zawahiri called "The Morning and the Lantern," in which he criticizes the Pakistani government. Zawahiri is believed to be in Pakistan.

Rehab El-Buri contributed to this report.

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