DAMASCUS, Syria — A powerful bomb rocked central Damascus on Tuesday, killing 13 people according to Syrian TV, and sowing fear and chaos in a busy commercial district of the capital for the second consecutive day.
The Syrian prime minister narrowly escaped an assassination attempt Monday after a car bomb struck near his convoy, a few kilometers (miles) away from Tuesday's blast.
The bombings appear to be part of an accelerated campaign by opposition forces seeking to topple President Bashar Assad to strike at his heavily protected seat of power.
"I heard a very loud bang and then the ceiling collapsed on top of me," said Zaher Nafeq, who owns a mobile phone shop in the Damascus Towers, a 28-floor office building. He was wounded in his hand and his mobile phone shop was badly damaged in the blast.
Syrian TV said Tuesday's explosion was caused by a "terrorist bombing" in the district of Marjeh, a commercial area in central Damascus. Assad's regime refers to opposition fighters as "terrorists."
There was no immediate claim of responsibility for the attack, which the TV said also wounded 70 people. Car bombs and suicide attacks targeting the Damascus and other cities that remain under government control in the third year of the conflict have been claimed in the past by the al-Qaida affiliated Jabhat al-Nusra group, which is fighting in Syria alongside rebels trying to topple Assad.
Damascus residents said they heard a powerful explosion and saw thick, black smoke billowing from behind a group of buildings.
The target of the attack was not immediately clear, although the explosion took place outside the former Interior Ministry building that was also damaged in the blast.
Ambulances rushed to the scene and Syrian state TV aired footage of fire trucks in central Marjeh Square and firefighters trying to extinguish a blaze that engulfed several cars and buildings.
A man was seen lying on the ground in a pool of blood while another, apparently wounded, was seen being carried by civilians into a bus.
Inspecting the site of the bombing on Tuesday, Interior Minister Mohammed al-Shaar, who himself escaped a car bomb that targeted his convoy in December, told reporters the back-to-back attacks in the capital were in response to the "victories and achievements scored by the Syrian Arab Army on the ground against terrorism."
With the recent influx of more advanced weapons and other foreign aid, the rebels have made significant gains in the south, seizing military bases and towns in the strategically important region between Damascus and the border with Jordan, hoping to eventually storm the capital from the south.
In a government counter offensive that involved ground troops and air power, Assad's troops have reclaimed much of the strategic territory in the past weeks, fortifying the defenses of the capital.
The Britain-based Syrian Observatory for Human Rights said 14 people were killed and 65 wounded in Tuesday's blast. The group, which relies on a network on activists based in Syria, often gives different casualty tolls from the figures released by the government. The discrepancy could not immediately be reconciled.
Local residents said they heard gunfire in the area of the attack immediately after the blast went off around 11:00 a.m., apparently meant to disperse people and open the way for ambulances. The residents spoke to The Associated Press on condition of anonymity, fearing reprisals from authorities for speaking to reporters.
The explosion underlined the tenuous security in the Syrian capital, just a day after a remotely detonated improvised explosive devise struck Prime Minister Wael al-Halqi's convoy. The premier escaped the assassination attempt in the capital's western neighborhood of Mazzeh, and state TV said al-Haliqi was not hurt in the bombing.
But a government official said two people were killed and 11 wounded in the assassination attempt. The official spoke to the AP on condition of anonymity because he was not authorized to give statements to reporters.
The Observatory said Monday's bombing killed at least five people, including two of al-Halqi's bodyguards and one of the drivers in his convoy.
The bombings laid bare the vulnerability of Assad's regime and highlighted an accelerating campaign targeting government officials, from mid-level civil servants to the highest echelons of the Syrian regime.
Syrian conflict began with largely peaceful anti-government protests in March 2011, but has since morphed into a civil war that has killed more than 70,000 people, according to the United Nations.
Also on Tuesday, Syrian troops battled opposition fighters near a military helicopter base in the northern province of Aleppo, killing 15 rebels in a single airstrike against their positions, according to Rami Abdul-Rahman, the Observatory's chief.
The rebels tried to storm the Mannagh base late Monday but the regime deployed fighter jets to the area, pounding rebel positions around the helicopter base, which is located near Syria's border with Turkey, said Rami Abdul-Rahman, the Observatory's chief.
Fighting was also raging Tuesday around other airports in the country, including the Damascus International Airport just south of the capital, Abdula-Rahman said.
In the north, rebels besieged military airport facilities, including Kweiras northeast of Aleppo city and the Nairab military base, adjacent to Aleppo's civilian airport, the country's second largest.
Activists in Syria, who are part of the Observatory's network of informants, also reported clashes around an air base in northern Idlib province and near air bases in the provincial capital of Dier el-Zour in the oil-rich province in Syria's east, along the border with Iraq.
The air power is Assad's greatest advantage in the civil war and the Syrian leader has exploited it to push back rebel advances and prevent the opposition from setting up a rival government in its northern stronghold.
In recent months, large parts of northern Syria near the border with Turkey have fallen to the rebels, including several neighborhoods of Aleppo.Comment on this story
But the rebels have repeatedly complained to their Western backers that their weapons are no match for Assad's airpower. They say they cannot effectively hold on to territory they capture as long as Assad's regime maintains control of the skies.
Earlier this month, a U.S. rights group accused the Syrian regime of committing war crimes with indiscriminate airstrikes that have killed more than 4,000 civilians since summer.
Human Rights Watch said Assad's air force has dropped "imprecise and inherently indiscriminate" munitions, including cluster bombs, on civilian areas, hitting hospitals, bakeries and residential buildings.
Associated Press Writers Barbara Surk and Bassem Mroue in Beirut contributed to this report.