Flashpoint / Evan Kohlmann

San Diego native Jehad Marwan Mustapha, at right, is believed to be the disguised English speaker who appeared in a recent video produced by the Somali Islamic terrorist group al Shabab.

The suicide bombing last weekend in Mogadishu – allegedly by a Somali American from Minnesota – has highlighted the important role played by U.S. citizens in the operations of al-Shabab, the Islamic terrorist organization battling the government in the war-torn east African nation.

FBI/AP

An FBI handout photo shows Abdisalan Hussein Ali, a Somali American who was 19 when he disappeared from Minnesota in November 2008. It is now suspected that he carried out a suicide attack against an African Union base in the Somali capital, Mogadishu, on Saturday.

If it is confirmed that Abdisalan Hussein Ali was one of two suicide bombers who attacked an African Union base, killing themselves and eight others, it will have been the third suicide bombing carried out in Somalia by Americans since 2008.

And U.S. officials tell NBC News that at least two members of the al-Shabab hierarchy are American-born, 20-something college dropouts, one of whom may be in the group’s “inner circle.”

U.S. officials and counterterrorism analysts estimate there are at least 40 Americans fighting with al-Shabab in Somalia, as well as another 200 with passports that would permit them to enter the U.S. without a visa.  

Many of the al-Shabab soldiers are Somali-Americans, many of them from the Minneapolis area, like Ali. The two leaders are not. They are Arab-Americans who traveled to Somalia in the latter part of the last decade and began rising in the ranks of the al-Qaida-linked terrorist group.

Feisal Omar / Reuters file

American born Islamic militant Omar Hammami, now known as Abu Mansoor al-Amriki, vows to avenge the death of al-Qaida leader Osama bin Laden at a news conference at a news conference farm in southern Mogadishu's Afgoye district on May 11, 2011.

One — San Diego-native Jehad Marwan Mustapha — is believed to be part of the group’s senior leadership. The other, Omar Hammami, is a unit commander.

Hammami's role has long been known. The 27-year-old from a suburb of Mobile, Ala., was profiled in the New York Times Sunday Magazine last year and has appeared in a number of al-Shabab videos, including one where he rapped an English-language recruiting pitch.

Hammami, whose father is Syrian, joined al-Shabab in late 2006 and took the name “Abu Mansoor al-Amriki,” or Abu Mansoor the American.

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He was interviewed in October 2007 by al-Jazeera, which identified him as a spokesman for the group, then indicted two months later by a federal grand jury on charges of material support for terrorism. He has since released four video and audio messages, most recently in April, when he mocked reports of his death and made his hip-hop recruiting pitch.

Mustapha, 29, is less well-known and has a less public role in al-Shabab, but is likely more influential in the terrorist group, according U.S. officials and Evan Kohlmann, an NBC News terrorism analyst.

“Though his name is perhaps lesser known than that of American national Omar Hammami, Jehad Mustapha is nonetheless reputed to be among the very top leaders of the foreign jihadists fighting alongside Shabab al-Mujahideen in Somalia under the banner of al-Qaida,” Kohlmann said.

One U.S. counterterrorism official, who like the others in this article spoke on condition of anonymity, referred to Mustapha as a “pretty bad dude” who has been with al-Shabab for “several years … long enough to be a significant commander … a senior player in the organization.”

Al-Shabab recently released video of a heavily masked, blue-eyed man speaking in American-accented English at a charity event in southern Somalia, and identified him as a representative of al-Qaida. Officials believe that the man could be Mustapha, who was indicted in the U.S. in August 2010 on charges of providing material support to terrorists.

In Somalia, Mustapha served under Saleh Nabhan, a senior al-Qaida and al-Shabab operative killed in a Navy SEAL operation in September 2009. 

There are conflicting reports on whether he had contact with Anwar al-Awlaki, the late New Mexico-born leading member of al-Qaida in the Arabian Peninsula, who was killed by a U.S. drone strike in Yemen in September.

Mustapha lived in San Diego through his late teens, when al-Awlaki was preaching in the city and is known to have had contact with other young jihadists, including two 9/11 hijackers, before leaving San Diego in 2002.

One U.S. official who spoke with NBC News said there is evidence to suggest contact, while declining to characterize it. A second official said he was unaware of any such connection.

Kohlmann said he also had no information indicating a connection, but added, “It’s not the most far-fetched thing I've ever heard.”

Before he was radicalized, Mustapha was working through his way through the University of California, San Diego, by manning the front desk at an auto repair shop.

By all accounts the son of working-class parents was responsible and easy-going. He was interested in business, majoring in economics.

Then, after marrying a Somali woman, he picked up and headed for her homeland. Now, say U.S. officials, when suicide bombers are dispatched to carry out their attacks, it's likely Mustapha is aware of it.