Syrian authorities on Thursday sent text messages over cell phones nationwide with a message for rebels fighting President Bashar Assad's regime: "Game over."

The messages signed by the Syrian Arab Army also urged the rebels to surrender their weapons and warned the countdown to evict foreign fighters has begun. The texts appear to be part of the regime's psychological battle against the rebels, but are highly unlikely to have any effect on fighter's intent on toppling Assad.

Syrians say they began receiving the messages a day after rebels bombed a military command center in Damascus - a major security breach of the heavily guarded capital that highlighted the regime's growing vulnerability in the face of a rebellion growing in confidence and capabilities.

People with cellular subscriptions received the messages while those with prepaid phones did not, residents in the Syrian capital said.

In August, Syrian army helicopters dropped leaflets warning rebels in Damascus to hand over their arms and seek amnesty.

Earlier Thursday, a Lebanese TV station broadcast footage showing Syrian government troops driving rebels from a building they had briefly occupied a day earlier after the double car bomb attack in Damascus.

The images from Lebanon's Al Manar TV station further demonstrated the scale of the security breach of the heavily guarded capital by rebels determined to topple the Assad regime.

The fighters detonated car bombs that engulfed the army headquarters in flames, followed by three hours of gunbattles in and around the compound Wednesday.

The government said four army guards were killed and 14 people were wounded, including civilians and military personnel.

The carefully orchestrated attacks were the most dramatic security breach in the center of the capital Damascus since July, when rebels detonated explosives inside a high-level crisis meeting in Damascus that killed four top regime officials, including Assad's brother-in-law and the defense minister.

They highlighted the regime's growing vulnerability, even as the 18-month battle to bring down Assad is locked in a stalemate.

Al Manar is owned by the Lebanese Hezbollah militant group, a strong ally of Assad's regime. Syrian state-run media, however, reported only on the car bombs, omitting any mention of clashes inside the building.

An Islamist militant group claimed responsibility on Thursday for an attack, according to a statement posted on the Internet.

The Al Nusra Front said Wednesday's assault was carried out in two stages, starting with a suicide bomber detonating a car near the building. It said four suicide attackers posing as security guards entered the compound in a second vehicle, seized the first floor and engaged soldiers inside before detonating their car, setting the building on fire. The statement, which featured photos of the building on fire, said all five militants died in the attack.

The Free Syrian Army, the main rebel force in an 18-month-old revolt against President Bashar Assad, has also said it was behind the attack and that dozens of people were killed. The Syrian army said four guards were killed and 14 wounded in what it described as suicide attacks, and that no senior officers were among the casualties.

Al Nusra has claimed a number of major attacks in Syria in recent months, including a raid and bombing of a pro-government Syrian TV channel headquarters in July and twin bombings in Damascus that killed 55 people in May.

Despite the high-profile attack, the two sides have been locked in a stalemate after 18 months of conflict. Activists say the death toll since the conflict began in March last year has recently topped 30,000, with nearly two-thirds of the casualties reported in the past six months.