Story highlights Clashes had quieted by day's end, witness say

At least 15 injured in clashes, a government official says

Four have been killed and nine injured in the attack, a ministry official says

President Ali Abdullah Saleh was toppled this year; his son still heads the Republican Guard

Hundreds of Republican Guards loyal to Yemen's former president attacked the Defense Ministry building near the center of the capital city of Sanaa on Tuesday, a Defense Ministry official said.

Four people were killed and nine others injured in the attack, said the official, who did not wish to be named because he is not authorized to speak to the media.

The Interior Ministry deployed 240 members of the central security forces to reinforce security at the Defense Ministry, he said.

"Senior military leaders intervened to help put an end the clashes, at least for the meantime," a senior Defense Ministry official told CNN.

Nearby banks have been shut down amid fears that the gunmen could storm them. At least 15 people were injured in the clashes.

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Violence continued into the afternoon between Defense Ministry security officers and hundreds of Republican Guard forces as heavy explosions were heard throughout Sanaa, witnesses said.

The clashes inched closer toward the center of the capital, the witnesses added. But the violence had quieted down by day's end.

Residents had tried to leave the area but couldn't because of the violence, they said, adding that bullets had entered many people's homes.

Ali Abdullah Saleh, Yemen's longtime president, stepped down this year after more than a year of clashes between his supporters and opponents. His son Ahmed Ali Saleh is head of the Republican Guard.

Yemeni opposition figures had been calling for his dismissal for months.

The top ranks of the elite force fear that the new president, Abdu Rabu Mansour Hadi, will sack them, particularly after Egypt's new president, Mohamed Morsy, pushed the country's top two military officers into retirement this weekend.

Hadi is in Saudi Arabia as the Organization of the Islamic Conference meets to discuss Syria and other regional issues.

He left Yemen on Monday.