Hezbollah lost four fighters to heavy clashes in the besieged Syrian city of Zabadani Thursday, as the group advanced with the Syrian army toward the city center from the west, Al-Manar TV and a security source said. The two allies captured the Othman and Rawdat al-Baraem al-Khasa neighborhoods in the west of the city after fierce clashes with rebels, the Hezbollah-run Al-Manar said. The report was confirmed by a security source. The source said that the rebels were attempting to contact the Syrian army to negotiate a fresh cease-fire but were being stonewalled. Heavy fighting in Zabadani resumed Saturday after the collapse of a three-day cease-fire agreement that was brokered by Iran and Turkey. The agreement had called on rebels to halt their offensive on the Idlib villages of Kefraya and Foua, allowing supplies to enter, in exchange for the same in Zabadani. However, negotiations over the weekend to extend the agreement failed, with rebel sources active in Zabadani blaming that failure on Iran's insistence that people inside Zabadani be evacuated to the north. Since then, the Syrian army has targeted rebel positions in the villages of Madaya and Bukain, south of Zabadani, launching an aerial bombardment on Madaya Tuesday. Many rebels and their families who fled Zabadani had taken refuge in Madaya, which has also served as an important supply hub for fighters inside the besieged city. A security source told The Daily Star that 11 rebels surrendered, while four were killed in heavy clashes over a 24-hour period, Tuesday to Wednesday. The heavy shelling on Madaya is purportedly to pressure rebels to ease their attacks on of Kefraya and Foua. Hezbollah's offensive to retake Zabadani, considered the last significant rebel stronghold on the Lebanese-Syrian border, was launched in June.