BEIRUT - Syrian regime forces faced fierce resistance from jihadists as they fought to capture a key airbase in the northwestern province of Idlib on Thursday, a monitor said.
Russia-backed government forces on Wednesday battled their way into the Abu Duhur military airport as they pressed a weeks-long battle in the last province beyond their control.
Idlib province is almost entirely held by Hayat Tahrir al-Sham, a jihadist outfit dominated by Al-Qaeda's former Syrian affiliate.
Government fighters have seized a string of villages in the southeast of the province since launching their offensive on December 25.
But on Thursday, Hayat Tahrir al-Sham and its Islamist allies led a counter-attack, retaking several villages from the regime, according to the Syrian Observatory for Human Rights.
Sixteen jihadists and rebels were killed in the counter-attack as they sought to cut off regime forces at the airport from their rear bases, the Britain-based war monitor said.
On Wednesday, 35 soldiers were killed at the airport, according to the Observatory.
The regime lost control of the Abu Duhur airbase in 2015 after a two-year siege by jihadists, with only the Shiite villages of Fuaa and Kafraya remaining under its control in the whole province.
Idlib's few rebel groups and Hayat Tahrir al-Sham have set aside their differences to fight President Bashar al-Assad's forces.
The regime hopes to seize control of southeast parts of Idlib province to secure a main road between the capital Damascus and the northern city of Aleppo.
Nearly 100,000 people have been displaced since early December by the fighting, the United Nations says.
More than 340,000 people are estimated to have been killed in the Syrian war, which began in 2011 as the regime brutally crushed anti-government protests. Millions have been displaced.