Seven people were arrested Monday on suspicion of involvement in attacks against a residential complex for Westerners in Yemen's capital, a security official said.

The official said some of those detained may have connections to al-Qaida, but he did not elaborate. He spoke on condition of anonymity because he was not authorized to talk to the media.

Several explosions shattered windows at the complex in the upscale Haddah neighborhood in San'a on Sunday. Nobody was injured, but Western residents were seen evacuating the compound shortly after the attack with suitcases and boxes. A heavy security presence blanketed the area, with troops patrolling roads leading to the U.S. and British embassies.

The State Department reacted to the attack Monday by ordering its "non-emergency" American employees at the U.S. Embassy in the capital of San'a and their families to leave Yemen. In a statement, the department also called on American civilians to defer any nonessential travel to Yemen.

"The security threat level remains high due to terrorist activities," the statement said. "The department remains concerned abouit possible attacks by extremist individuals or groups against U.S. citizens, facilities, businesses, and perceived interests."

The security official did not release the names of the seven detained, and it was unclear if they were suspected of directly belonging to al-Qaida. Authorities have not yet blamed the terror network for the attack, the official said, adding that authorities were searching for three other suspects.

A little-known group purportedly with al-Qaida links claimed later Monday it was behind the attack, launched allegedly in revenge for the slaying last year of Taliban military commander Mullah Dadullah in Afghanistan.

The Jund al-Yemen Brigades said in a statement, obtained by the Washington-based SITE group that monitors terror traffic on the Internet, that they had fired three mortar shells at the compound. The statement's authenticity could not be independently verified.

Jund al-Yemen has claimed past attacks but al-Qaida has never confirmed any affiliation to the group and its postings have not carried routine markings of the terror network's media arm.

Despite government efforts to fight the network, al-Qaida has an active presence in Yemen, the poorest country in the Arab world and the ancestral home of Osama bin Laden. Al-Qaida was blamed for the 2000 bombing of the USS Cole in the Yemeni port of Aden that killed 17 American sailors.

Yemen is also grappling with violence in the south, where security forces have been trying to put down riots by thousands of former southern army officers, political activists and unemployed men who have accused the government of unequal treatment.

A Yemeni soldier was killed Monday in the rioting, security officials said. Nineteen other people — soldiers and civilians — were wounded in continued clashes across several southern provinces.

Residents said government forces fired live bullets and tear gas on demonstrators in the Abyan, Aden, al-Dhale' and Lahij provinces.

The rioting has underlined increasing tensions between southern and northern Yemen, 14 years after a civil war. The protesters have been largely members of the army of south Yemen who were ousted after being defeated by northern forces.

Four people have died since the violence broke out early this month, and scores of protesters have been arrested.