Russian forces bombed a key bridge and highway to try and slow a lightning advance by rebels toward the Syrian city of Homs as thousands fled the area.
The U.K.-based Syrian Observatory for Human Rights monitoring group said civilians were fleeing from Homs towards the Mediterranean coastal regions of Latakia and Tartus, strongholds of the government and the site of Russian air and naval bases.
The United Nations said on December 6 that almost 300,000 people in Syria had already been displaced since late November by the fighting, and that up to 1.5 million could be forced to flee as the rebels advance and deal losses to the country's president, Bashar al-Assad, as well as his allies in Russia and Iran.
Assad has relied on Iran and Russia to remain in power since the conflict erupted in 2011.
A Syrian Army officer was quoted by Reuters as saying that Russian bombing overnight had destroyed the Rastan bridge along the key M5 highway linking Homs to Hama, another city the rebels captured a day earlier.
The rebels, led by Islamist group Hayat Tahrir al-Sham (HTS), have made major advances over the past several days, including the capture of Aleppo, the country's largest city, as well as 14 central villages and towns, and gotten as close as 35 kilometers from the Russian-operated Khmeimim air base.
HTS is considered a terrorist group by the United States, Britain, Canada, and the European Union.
Hama, Syria's fourth-largest city, is key to the defense of Damascus and the gateway to the coastal cities of Tartus and Latakia, the former being home to a strategic Russian naval base.
In his first media interview in several years, Abu Muhammad al-Julani, the group's leader, told CNN the goal "remains to overthrow the Bashar al-Assad regime, and it is our right to use all available means to achieve this goal."
Besides HTS, the rebels also include an umbrella group of Turkish-backed Syrian militias called the Syrian National Army.
The foreign ministers of Iraq, Syria, and Iran were to meet on December 6 to discuss the situation, while Russian Foreign Ministry spokeswoman Maria Zakharova said the top diplomats from Moscow, Tehran, and Ankara will meet in Qatar on December 7.
The state news agency TASS reported on December 6 that Russia's embassy in Syria had urged Russian nationals to leave the country due to the situation.