(CNN) -- Syria's prime minister became the highest-profile official to leave the embattled regime of Bashar al-Assad on Monday.

Opposition leaders said Riyad Hijab had defected, while Syrian state television said al-Assad dismissed Hijab from his post Monday.

There were conflicting reports about the whereabouts of Hijab, who was appointed prime minister in June.

A Syrian opposition official, Muhammad el-Etri, told CNN that Hijab had defected, was "in a country neighboring Syria" and would be heading to Qatar "sometime soon."

"I announce today my defection from the killing and terrorist regime and I announce that I have joined the ranks of the freedom and dignity revolution. I announce that I am from today a soldier in this blessed revolution," Hijab said in a written statement read by el-Etri on Al Jazeera on Monday.

Government officials announced Hijab's sacking after officials discovered he had left Syria, el-Etri said.

George Sabra, a spokesman for the opposition Syrian National Council, said Hijab fled Syria overnight and arrived with his family in Jordan.

Jordanian government spokesman Samih Maaytah said Hijab had not entered the country's territories, according to state television. But a senior Jordanian official told CNN that Hijab had defected to Jordan and was with his family.

In July, one of Syria's most senior diplomats -- Nawaf al-Fares -- defected, publicly embraced his country's uprising and called for a foreign military intervention. Al-Fares was 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 after the parliamentary elections and was tasked with creating a new Cabinet for al-Assad's regime.

Opposition leaders haled the news of Hijab's defection.

"We consider the defection to be what is morally right and what is called for at this historic time," said Abdulbaset Sieda, head of the Syrian National Council. "This is a killer and criminal regime, and at this historic moment, there should be no further hesitation. It is imperative to stand by the people of Syria now."

Meanwhile, fighting raged in northern Aleppo, Syria's most populous city.

Snipers fired from the roofs of buildings and artillery fire rang out in the besieged neighborhood of Salaheddin.

CNN's Ben Wedeman said drivers had to dodge piles of rubble in the streets. Residents evacuating to safer neighborhoods left their homes with all the belongings they could carry, he said.

An elderly man, carrying a briefcase and a bag full of jam, said he was leaving the neighborhood to move in with his daughter.

"What kind of leader does this to his own people?" the man said as he left his home.

Heavy shelling was reported in several neighborhoods in northern and central Aleppo.

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, some 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 84 people were killed in fighting across the country Monday, the opposition 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.

CNN can not independently confirm reports of violence, as the government has severely restricted access to Syria by international journalists.

There were reports of a bombing 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 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 on state-run TV.

Over the weekend, United Nations Secretary-General Ban Ki-moon said that the situation may get worse in Aleppo, describing the city 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.

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, Salma Abdelaziz, Barbara Starr and Elise Labott contributed to this report.