By Bloomberg

Al-Shabaab, the Somali terrorist group behind a four-day attack on a Nairobi shopping mall, threatens U.S. embassies and interests in Africa and potentially on U.S. soil as well, counterterrorism analysts told Congress.

The Westgate Mall attack last month showed al-Shabaab’s growing capacity to conduct sophisticated operations requiring careful planning and reconnaissance, Seth Jones, associate director for international security and defense policy at Rand Corp., told the House Foreign Affairs Committee.

That ability, coupled with the group’s use of online social media and “Jihad rap” recruitment videos on Google Inc. (GOOG)’s to attract young Americans, is a concern, Jones said at a panel hearing yesterday.

“Al-Shabaab has the capacity to strike outside Somalia,” he said. “They have an interest in targeting the United States, and three, they’ve been recruiting inside America. You put all those together and, yes, there’s reason for concern.”

The al-Qaeda affiliate controls large parts of southern Somalia and imposes an extreme version of Sharia law, including stoning women accused of adultery and amputating hands to punish theft. Even as al-Shabaab has lost control of territory, Jones said, it has maintained its operational capability.

Attacking Kenya

By 2012, almost a quarter of the group’s attacks targeted Kenya, which contributed troops to a United Nations peacekeeping mission in Somalia, known as AMISOM and operated by the African Union. As part of its duties, AMISOM supports the Somali government that al-Shabaab seeks to topple.

While Jones said the group hasn’t shown interest in exporting terror attacks to the U.S. right now, he and other witnesses told the committee about the risk that Somalis already in the U.S. could become part of a domestic plot.

There are 50 American members of al-Shabaab and there may be more, said Representative Michael McCaul, a Texas Republican.

An Alabama man known as Abu Mansoor Al-Amriki, or “the American,” helped lead the group until internal disputes led to his death last month in an ambush in Somalia that the Associated Presssaid was ordered by al-Shabaab. The U.S. Somali population is estimated at 100,000 by the U.S. Census Bureau.

“The risk to the homeland is definitely there,” said Don Borelli, chief operating officer of the Soufan Group, a New York-based consulting firm that provides strategic intelligence services to governments and businesses. “I don’t know if it’s higher today than it was a month ago.”

Domestic Risk

Borelli told the committee he fears that if radicalized Somali-Americans hold a U.S. “blue passport, they can come back and re-integrate and we have a very dangerous situation.”

The militia’s diffuse leadership structure makes it harder to dismantle or destroy, David Kilcullen, a former U.S. State Department adviser on counterterrorism, said in his book, “Out of The Mountains: The Coming Age of the Urban Guerrilla.”

While the Pakistan-based militant group Lashkar-e-Taiba kept its command center in Pakistanduring the 2008 Mumbai terror attack, “the Somali militia made their command and control node invulnerable by not having one,” Kilcullen said.

Al-Shabaab has carried out almost 550 terrorist attacks since 2007, according to the National Consortium for the Study of Terrorism and Responses to Terrorism, in College Park, Maryland.

Representative Ted Poe, a Texas Republican who leads the Foreign Affairs subcommittee on terrorism, expressed concern that al-Shabaab had easy access to U.S.-run media such as Twitter Inc.’s microblogging site. The group used messages to goad Kenyan officials while the mall attack was under way. The assault left 69 dead, hundreds wounded and dozens missing, according to the Kenyan Red Cross.

Twitter Concern

“Twitter claims it doesn’t allow terrorists to use the account,” Poe said, citing a law that forbids support for terrorist groups.

“Either way, Twitter should be taking down terrorist accounts,” Poe said. “It’s time for Twitter to stop violating the law.”

Nu Wexler, a Twitter spokesman, said, “We do not comment on individual Twitter accounts, for security and privacy reasons,” in an e-mail.

Rules postedon the San Francisco-based company’s website tell users, “You may not publish or post direct, specific threats of violence against others.”

Witnesses at the hearing yesterday stressed al-Shabaab’s command of social media.

“Al-Shabaab means ‘the youth,’” said Richard Downie, deputy director of the Africaprogram at the Center for Strategic and Independent Studies, a Washington research group. “It attracts a lot of people who are media-savvy and uses media to powerful effect.”

The Internet’s reach allows al-Shabaab to recruit globally.

“The Internet does not know the boundary between Somalia and San Diego,” Borelli said. The U.S. shouldn’t make the same mistake it made in the early days of al-Qaeda and “see it only as a local group,” he said.