BEIRUT -- The main Western-backed Syrian opposition group elected a former political prisoner Saturday as its new president, filling a post that has been vacant for months due to divisions among President Bashar Assad's opponents.

Inside Syria, government troops advanced into rebel-held areas of the central city of Homs, pushing into a heavily contested neighbourhood after pummeling it with artillery that drove out opposition fighters, an activist said Saturday.

The Syrian National Coalition said in a statement that Ahmad al-Jarba received 55 votes from the 114-member council in the poll that took place in the Turkish city of Istanbul, where many Syrian opposition figures are based.

Al-Jarba is from the northeastern province of Hassakeh, and is a member of the powerful Shammar tribe that extends into Iraq. He and other SNC members could not be immediately reached for comment Saturday.

The opposition coalition also elected three vice-presidents including Mohammed Farouk Taifour, a senior official with Syria's Muslim Brotherhood. The other two vice-presidents are Salem al-Mislit and prominent opposition figure Suhair Atassi. Badr Jamous was voted in as the SNC's secretary general.

The SNC meeting is the second attempt in recent months by Assad's opponents to unify their ranks. The opposition bloc is primarily composed of exiled politicians with little support among Syrians inside the country who are trying to survive the third summer of conflict that has killed more than 93,000 people and forced millions to flee their homes.

In late May, the opposition leaders met for more than a week in Istanbul, but failed to elected new leaders or devise a strategy for possible peace talks that the U.S. and Russia have been trying to convene in Geneva. The election of al-Jarba suggests that the opposition is trying to unite despite its differences after Assad's forces have gained ground in and around the strategic town of Qusair near the border with Lebanon.

The vote also comes as the U.S. and Russia hope to bring the sides together at an international conference in Geneva. The SNC said recently it will not attend the Geneva talks unless they are about Assad handing over power.

Assad repeatedly has dismissed his political opponents as foreign-directed exiles who don't represent the people of Syria. The president also has shrugged off international calls to step down, saying he will serve the rest of his term and may consider running for another one in next year's presidential elections.

On the ground in Syria, meanwhile, troops gained ground in the rebel-held Khaldiyeah district of the city of Homs. The push into Khaldiyeh was the first significant gain in the city for Assad's forces. Government troops have been waging an eight-day campaign to seize parts of the central Syrian city that has been in rebel hands for more than a year.

Tariq Badrakhan, an activist based in the neighbourhood, said government troops used rockets, mortars and cannon fire to flush out the area's "first line of defences" on Friday evening. The offensive continued Saturday morning, he said via Skype, as explosions were heard in the background.

"We feel like they are shaking the sky," Badrakhan told the AP.

Another activist said eight rebels were killed in the fighting. He requested anonymity because rebels have accused him in the past of damaging their morale by reporting their casualties. He could not confirm that government forces had entered Khaldiyeh but said it was consistent with the fighting he was following there. State-run media said government forces had seized buildings in the nearby Bab Houd area.

Fighting also continued Saturday in the northern city of Aleppo, a crucial stronghold for the rebels, as well as the Damascus suburb of Qaboun.

The Syrian conflict, which began with months of peaceful protests against the Assad regime two years ago, deteriorated into an all-out civil war after a violent government crackdown.

Government forces, sometimes backed by fighters of the Lebanese Shiite militia Hezbollah, have launched a major countrywide offensive to reclaim territory lost to rebels, who operate in chaotic groups with ideologies ranging from secular to hardline Islamic extremists. Hardline Sunni Muslims from other countries have also joined the fighting.