Fierce gunbattles have remained unrelenting across Syria, as forces loyal to President Bashar al-Assad seized a strategic town east of Damascus, state media and opposition activists have said.
Activists and fighters said on Wednesday that the army had entered the town of Otaiba, which has been used by rebels as a weapons supply route for the past eight months.
"The disaster has struck, the army entered Otaiba. The regime has managed to turn off the weapons tap," a fighter from the town told Reuters via Skype.
Rebels said they had pulled out of the town, a gateway to the eastern rural suburbs of Damascus known as al-Ghouta, in the early hours on Wednesday after more than 37 days of fighting in which they accused the government of using chemical weapons against them twice.
The government has denied using chemical weapons and accused rebels in turn of firing them in Aleppo.
"Now all the villages will start falling one after another, the battle in Eastern Ghouta will be a war of attrition," another fighter in the area said, speaking by Skype.
The heavy gunbattle in Otaiba was just part of the wider devastation caused by the conflict, which began more than two years ago and already killed more than 70,000 people, and displaced more than a million people.
Elsewhere, Syrian rebels have fired shells hitting the Lebanese border region Hermel, a bastion for the Lebanese Shia movement Hezbollah, in what they said was retaliation for strikes by the group.
On Tuesday, two new mortar rounds hit the city of Hermel, causing light damage to a house there, while raising fears that Lebanon is being drawn further into the Syrian conflict.
Rebels have threatened to "move the battle into Lebanon" if the Syrian government offensive, which they described as Hezbollah-led, continues.
Hezbollah has said those fighting are Lebanese party members who have lived in Syrian border villages for decades and are defending themselves against "rebel attacks".
Meanwhile, sheikh Ahmad al-Assir, a controversial Lebanese Salafist, has urged his followers to join Syrian rebels fighting troops loyal to Assad and Hezbollah.
The call came as a second Sunni Lebanese sheikh called the fight against Assad's regime a "jihadist duty".
"Today, everyone recognises the danger posed by the intervention of [Hezbollah chief Hassan] Nasrallah and his shabiha [pro-Assad militia] in Syria," Assir, who is based in the southern Lebanese city of Sidon, told his followers late Monday.
Syria's opposition and monitoring groups have accused Iran-backed Hezbollah of sending elite fighters to battle alongside regime troops in al-Qusayr, an area of Syria's central Homs province near the Lebanese border.
"Nasrallah and his shabiha have taken the decision to enter into these areas [Qusayr] in order to massacre the oppressed people there," Assir added.
"There is a religious duty on every Muslim who is able to do so... to enter into Syria in order to defend its people, its mosques and religious shrines, especially in Qusayr and Homs."