"We will get revenge," the militant Islamist Ansar al-Shariah, allied with al-Qaida's Yemeni branch, said in a statement posted on an al-Qaida Web site after a suicide bomber in the capital, Sanaa, killed as many as 112 Yemeni soldiers rehearsing Monday for a parade that was to celebrate Yemen's National Day Tuesday, the day North and South Yemen were unified as the Republic of Yemen in 1990.
Ansar al-Shariah, or "Partisans of Shariah," the moral code and religious law of Islam, claimed responsibility for the bombing, saying it was in retaliation for U.S.-assisted Yemeni offensives against its strongholds in southern Yemen.
Authorities said 19 soldiers and 33 militants were killed in the weekend clashes.
The central square suicide attack, in which an assailant dressed in an army uniform detonated a concealed bomb, injured at least 300 people, authorities said.
It was Sanaa's bloodiest bloodshed in years. The capital is heavily fortified and had been spared the worst of the insurgent violence.
It also came a day after gunmen fired on a car carrying three U.S. civilian contractors training the Yemeni coast guard in the Red Sea port of Hudaydah, Yemen's fourth-largest city.
The Pentagon said the three contractors suffered minor injuries.
President Abdu Rabbo Mansour Hadi, in office since Feb. 27, said in an address Monday night the "war against terror will continue until terror is uprooted and terminated, regardless of the sacrifices."
"We are determined to clear Yemen of extremists and free ourselves to face our economic and development challenges," he said after firing two top commanders, including the nephew of former President Ali Abdullah Saleh, who was deputy director of national security.
Yemeni Defense Minister Nasser Ahmed, who Ansar al-Shariah said on Facebook it had targeted for assassination, was in the square near the presidential palace to inspect the troops but was not hurt, officials said.
Earlier this month, a U.S. drone strike killed Fahd al-Quso, an al-Qaida operative believed to have plotted the bombing of the U.S. destroyer USS Cole in 2000 that killed 17 American sailors.