Syria's prime minister leaves regime

• NEW: Riyad Hijab's defection is the highest profile departure
• Syria's prime minister defects to Jordan, the opposition says
• Syrian state-run TV reports the prime minister resigned
• Hijab became prime minister in June after serving as minister of agriculture

(CNN) -- Syria's prime minister has defected, the opposition said Monday, in what is the highest profile departure from the embattled regime of President Bashar al-Assad.

Riyad Hijab, who was appointed prime minister in June, fled Syria overnight, arriving with his family in Jordan, said George Sabra, a spokesman for the opposition Syrian National Council.

The government, meanwhile, said Hijab resigned his post, according to a banner on Syrian state-run TV.

CNN cannot independently confirm the report as access to Syria by international journalists has been severely restricted by the government.

Hijab will hold a press conference later Monday, Sabra said.

In July, Syria's most senior diplomat -- Nawaf al-Fares -- defected, publicly embraced his country's uprising and called for a foreign military intervention. Al-Fares served as Syria's ambassador to Iraq.

Manaf Tlas, a Sunni general in Syria's elite Republican Guards, also defected last month. Tlas is the son of a former defense minister and a cousin of a first lieutenant in al-Assad's army.

Hijab, just like al-Fares and Tlas, is a Sunni who served in a power structure dominated by the Alawite minority, an offshoot of Shiism.

Hijab became prime minister in late June following the parliamentary elections and was tasked with creating a new cabinet for al-Assad's regime.

The news came amid reports of a bomb explosion Monday inside the Syrian state-run TV building in Damascus, the latest in a series of attacks to rock the nation's capital city as Syrian rebels and government forces battle for control of the country.

There were reports of injuries in the explosion that comes as al-Assad's forces fight to keep control of its main cities -- Damascus and Aleppo -- in the more than year long uprising.

There was no immediate claim of responsibility for the blast, which occurred on the third floor of the Public Center for Broadcast in Television.

"All employees of the Public Center for Broadcast in Television are well, and we know who stood behind this cowardly brutal attack. There are some injuries but Syrian media will continue to broadcast," the Ministry of Information said in a statement on state-run TV.

The explosion came amid reports of renewed fighting early Monday in Aleppo, Syria's most populous city, according to the opposition.

At least 44 people were killed in fighting across the country on Monday, the Local Coordination Committees of Syria said. The deaths included 10 people killed in fighting and the discovery of 20 bodies in Aleppo, the group said.

The reports of deaths follows news that warplanes pounded rebel strongholds in the city north of Damascus, and heavy shelling was reported in several neighborhoods in northern and central Aleppo.

CNN can not independently confirm reports of violence as access to the country has been severely restricted by the Syrian government.

Bashir Al-Hajji, a spokesman for a Free Syrian Army brigade in Aleppo said clashes raged for hours at various spots near the city center, including close to the presidential palace.

Al-Hajji says he is in the Industrial City of Aleppo, about 15 kilometers (nine miles) from the city of Aleppo, which is the commercial capital.

As rebels scrambled to fend off regime forces in Aleppo, fighting was reported in other parts of Syria.

At least 124 people were killed across the country on Sunday, the opposition Local Coordination Committees of Syria said. The deaths included 59 in Damascus and its suburbs and 25 in Aleppo, the group said.

United Nations Secretary-General Ban Ki-moon said the situation may get worse in Aleppo, describing it as "the epicenter of a vicious battle between the Syrian government and those who wish to replace it."

Through much of the uprising that began last year, Aleppo remained relatively free of violence. That changed this summer with the influx of rebels into the city.

On Sunday, state-run news agency SANA said Syrian forces were continuing to chase "Gulf and Turkish militias" in Aleppo neighborhoods.

Rebels have launched their own attacks in multiple neighborhoods.

That included a brazen push Friday to seize a state-run broadcasting building. Rebels pushed into the radio and TV complex, and took over parts of it, before eventually withdrawing because of snipers and military shelling, the LCC said.

Around Syria's capital, "armed terrorists" attacked a bus carrying 48 Iranian Shiite pilgrims and kidnapped them, Iranian state media said. Syrian state media also reported the abduction and said it is under investigation.

It is unclear whether the hijacking is linked to the uprising against the Syrian government. The Iranian government is an ally of the al-Assad regime, which has been fighting a rebel movement dominated by Sunnis.

Iranian Foreign Minister Ali Akbar Salehi lashed out at Arab media outlets over the weekend over reports that suggested those kidnapped were not pilgrims but rather members of the Iran's revolutionary guard.

The reports, Salehi said, have "no legal basis" and are the result of an irresponsible media, according to Iran's state-run IRNA news agency.

It was a claim that appears to have been first made in an online video that featured a commander of the Free Syrian Army who claimed the 48 people taken at gunpoint are revolutionary guards and not pilgrims. CNN cannot independently verify the authenticity of the video.

Salehi called on his counterparts in Qatar and Turkey to help work for the release of the kidnapped pilgrims, according to IRNA, Tehran's state media.

Roughly 17,000 people have been killed since the Syrian conflict first flared in March 2011, when government forces began cracking down on protesters, Ban said last month. The opposition put the toll at more than 20,000.

CNN's Mohammed Jamjoom and Salma Abdelaziz contributed to this report.