Five people died Tuesday when soldiers loyal to the son of Yemen's ousted president attacked the Defense Ministry in Sanaa, clashing with the guards, military officials said.
The clash was part of an increasingly violent challenge to new presidential orders to restructure the military.
Soldiers from the Republican Guards, led by ex-President Ali Abdullah Saleh's son, were protesting a presidential decree that put some of the force's units under presidential or regional oversight.
It was the second time in less than a week that the ministry has been besieged by his forces.
The military officials said the attacking soldiers used automatic rifles and grenades. Troops responded, and the clashes killed one attacker, two ministry guards and two civilians.
The officials were speaking on condition of anonymity because they were not authorized to speak to reporters.
Tanks and armored vehicles moved in on the ministry and closed off streets leading to it and the nearby central bank.
U.S. State Department spokeswoman Victoria Nuland, speaking to reporters in Washington, urged an immediate end to violence and expressed support for the reforms introduced by the new president, Abed Rabbo Mansour Hadi.
"I'm not going to speak to the motivations of some of these guys who have been violent," Nuland said, "obviously it appears to be some of the dead-enders of the (former) regime trying to have their due and resist some of this democratic change that President Hadi is putting in place."
She said those resisting the changes are "on the wrong side of history."
On Friday, troops surrounded the ministry to protest the government's move to strip Saleh's son of his command of units of the Guard, the country's best-trained force. That siege ended after government forces threatened to open fire if the protesters didn't leave.