They have already captured the key cities of Aleppo in the north and Hama in the centre, dealing successive devastating blows to President Bashar al-Assad, nearly 14 years after protests against him erupted across Syria.
The Syrian Observatory for Human Rights, a UK-based war monitor, said thousands of people had begun fleeing on Thursday night towards Syria's western coastal regions, a stronghold of the government.
Thousands of people have been displaced as opposition groups seized territory in Syria. (AP PHOTO)
A resident of the coastal area said thousands of people had begun arriving there from Homs, fearing the rebels' fast-paced advance.
On Friday morning, Israeli air strikes hit two border crossings between Lebanon and Syria, Lebanon's transport minister Ali Hamieh said.
The Syrian state news agency said the Arida border crossing with Lebanon was out of service due to the attack.
The Israeli military said it had attacked weapons transfer hubs and infrastructure overnight on the Syrian side of the Lebanese border, saying these routes had been used by the Lebanese armed group Hezbollah to smuggle weapons.
Russian bombing overnight also destroyed the Rustan bridge along the key M5 highway, to prevent rebels using this main route to Homs city, a Syrian army officer told Reuters.
"There were at least eight strikes on the bridge," he said.
Government forces were working to beef up positions around Homs city with fresh reinforcements, he said.
Rebels led by the Islamist faction Hayat Tahrir al-Sham had pledged to move on to the central city of Homs, a crossroads city that links the capital Damascus to the north and Assad's heartland along the coast.
"Your time has come," said a rebel operations room in an online post, calling on Homs residents to rise up in revolution.
