Syrian rebels are reported to have forced government troops to retreat to the edge of the north-western region that is the heartland of President Bashar al-Assad’s Alawite sect.
A military source was quoted as saying the troops had taken up new defensive positions in the Sahl al-Ghab plain.
It lies just to the east of the coastal mountains where Mr Assad’s ancestral village of Qardaha is located.
The rebel advance is the latest in a series of setbacks for the president.
Last month, he acknowledged the army faced a manpower shortage and had withdrawn from some areas in order to defend those he considered most significant
IS ‘releases Assyrians’
The military source told the Reuters news agency that a large rebel force had seized high ground to the east of the Sahl al-Ghab following two weeks of fighting.
“The army – to avoid losses and to avoid exposure to artillery and missiles from these areas – has taken up a second defensive line… It has strengthened its positions in this second defensive line,” the source said.
“At the end of the day, it is giving up positions in the interest of strengthening and fortifying a fixed defence line.”
A rebel commander said the army had fallen back to the Alawite village of Jurin.
“The progress was – praise be to God – fast,” Abu al-Baraa al-Hamawi, a leader of Ajnad al-Sham, told Reuters. “As for the coming battle, we expect it will be more difficult because it will be in the stronghold of the regime.”
The rebels, from an alliance that includes the al-Qaeda-affiliated al-Nusra Front, have advanced from areas to the north-west which they captured from the government earlier this year.
The Syrian Observatory for Human Rights, a UK-based group that monitors the conflict in Syria, said the rebels had been using guided anti-tank (TOW) missiles supplied in large numbers since March by allied regional powers. The government had carried out heavy air strikes in an attempt to drive back the rebels, it added.
More than 230,000 people have been killed since the uprising against Mr Assad erupted in 2011. Some 11.5 million others – more than half of the country’s population – have fled their homes.
In a separate development on Tuesday, the so-called Islamic State (IS) released 22 Assyrian Christians the jihadist group took hostage from villages in north-eastern Syria in February, activists said.
Afram Yakoub of Assyrian Federation of Sweden told the BBC that all of those freed were elderly men and women, and that some of them also had health problems. IS continued to hold close to 200 other Assyrians, he added.