Shi'ite rebels ride on a truck outside the state television compound in Sanaa September 21, 2014. Khaled Abdullah Ali Al Mahdi/REUTERS Houthi fighters entered Yemen's presidential palace after a brief clash with the compound's security guards, witnesses and security sources told Reuters, a day after some of the worst battles in the capital in years.

With the Houthi rebels stripping down Yemen's existing state apparatus ever since marching into Sa'ana in September, some in the teetering Yemeni government are already characterizing the attacks on the presidential residence as an attempt to take over the country.

"This is a coup. There is no other word to describe what is happening but a coup," Saleh al-Jamalani, a Yemeni army colonel, told The Associated Press. He said that the rebels likely had the assistance of elements inside the current government, headed by president Abdu Mansour Haddi.

CNN quoted the Yemeni government's information minister calling the situation “the completion of a coup” and saying that the president had “no control.” The New York Times also reported that Haddi was inside of the presidential compound as it was being shelled, and that a US diplomatic vehicle briefly came under fire near a Houthi checkpoint.

Yemen, which borders Saudi Arabia to the south and is home to nearly 25 million people, was one of four countries to replace its leader during the "Arab Spring" uprisings, along with Libya, Egypt, and Tunisia. Now, it threatens to become another one of the region's violent political and military vacuums — with the added complication of Yemen's desert periphery being home to Al Qaeda's most capable foreign affiliate.

The Battle In Sa'ana

Guards at the presidential palace housing the main office of President Abd-Rabbu Mansour Hadi said they handed over the compound to Houthi fighters after a brief clash. Witnesses said there was a brief clash between a Houthi force and palace guards.

Witnesses also said they saw the Houthis seize armored vehicles that had been guarding the entrances to the palace.

Houthi fighters stand near a damaged guard post at a Presidential Guards barracks they took over on a mountain overlooking the Presidential Palace in Sanaa on January 20, 2015. Khaled Abdullah Ali Al Mahdi/Reuters The Houthis on Monday fought artillery battles with the army near the presidential palace, in some of the most intense fighting in Sanaa in years, and surrounded the prime minister's residence.

Nine people were killed and 90 wounded before a ceasefire came into force on Monday evening.

The Houthis are a community of Shi'ite Muslim tribes from Yemen's desert periphery. A Houthi insurgency has been ongoing for most of the last decade, and was sparked in the early 2000s by the largely Sunni central government's encroachment on traditional Houthi governance and traditional authority, along with the group's traditional marginalization within Yemen's politics.

Houthi fighters operate a checkpoint on a street leading to the Presidential Palace during clashes in Sanaa on January 19, 2015. Khaled Abdullah Ali Al Mahdi/Reuters But in the chaotic years after the resignation of long-serving president Ali Abullah Salih in early 2012 after a wave of Arab Spring-style street protesters, the Houthi uprising took on a national-level character, culminating in the rebels' march on Sanaa in September of 2014 and seizure of key government ministries. The Houthis then ordered a cabinet reshuffle in November after demanding a final say over Finance Ministry expenditures the month before.

The Houthis have also received forms of assistance from Iran as well, turning Yemen into the latest battleground between Tehran and the Middle East's Sunni states.

(Reporting by Sami Aboudi; Editing by William Maclean, Ralph Boulton)