Five people have been killed and at least nine have been wounded after hundreds of troops from Yemen's elite Republican Guard force attacked the headquarters of the defence ministry.
The forces, who were later repelled, were led by the son of ousted president Ali Abdullah Saleh.
The soldiers laid siege to the ministry in Sanaa on Tuesday before attacking it with machine guns and rocket-propelled grenades, witnesses said.
The attack comes a week after President Abd-Rabbu Mansour Hadi ordered a restructuring of army forces, reducing the number of units under the command of rival chiefs, including Saleh's son.
General Ahmed Ali Abdullah Saleh's forces, who blocked the roads leading to the ministry in central Sanaa, came from the main base of the Republican Guard in Sawad, south of the capital, witnesses said.
Troops guarding the ministry used armoured vehicles to chase the attackers, and were backed by military police and reinforcements from the army's fourth armoured brigade.
Army reinforcements were deployed around the residence of Hadi, who replaced Saleh in an Gulf-brokered peace deal that ended 13 months of protests against the veteran leader.
In a presidential decree last week, Hadi, who was in not in Yemen at the time of the attacks, ordered the formation of a "presidential protection" force that will include three brigades from the Republican Guard.
The force will also include a brigade from the first armoured division led by General Ali Mohsen al-Ahmar who defected to the anti-Saleh opposition last year, official sources said.
Hadi assigned other brigades from the two rival units to the central and southern regions.
Hakim Almasmari, editor in chief of the Yemen Post, told Al Jazeera that Tuesday's attacks were "a strong warning to Hadi".
"President Hadi left the country and hours later, the attacks took place. He's not safe - or his rule is not safe in Yemen," he said.
The US on Tuesday urged all sides in Yemen to show restraint and respect reforms by new President Abdrabuh
Mansur Hadi after troops attacked the defence ministry.
"We have been urging restraint on all sides, an immediate end to the violence and respect for President Hadi and the reforms that he is putting in place and the democratic transition," said US state department spokeswoman Victoria Nuland.
Source: Al Jazeera and agencies