AMMAN — Syrian warplanes attacked militant Islamists near the northern city of Aleppo on Sunday, both sides said, as the government tried to push back a major insurgent advance in the area.

Dozens of airstrikes hit near the town of Khan Touman, which rebels took from forces loyal to the government and its ally, Iran, late Thursday, insurgents and state media reported.

Aleppo — one of the biggest strategic prizes in a war now in its sixth year — has been divided into government and rebel-held zones through much of the conflict. The surrounding region is also crossed by valuable supply routes into neighboring Turkey.

Syria's army said it had hit "terrorist groups" hard Sunday but did not give details of any territorial gains.

Manar, the media outlet of the Iran-backed Hezbollah group supporting Syrian government forces in the area, said heavy fighting was ongoing against the hardline Sunni Muslim rebels.

Government forces had made significant advances in the northern region after their other main ally, Russia, entered the war in September.

But the seizure of Khan Touman on Thursday by an alliance of extremist insurgents known as Jaish al-Fatah, including the al Qaeda-linked Nusra Front, marked a major counterattack by forces opposed to president Bashar Assad.

The loss of the town south of Apello was a particular blow for Iranian troops, who suffered one of their biggest single-day losses in the conflict.

A fighter from the Nusra Front — which is not involved in the shaky ceasefire across Syria — said on social media it was now pushing further south toward the town of al Hader, a major stronghold for Hezbollah and Iranian forces.

Separately, Amaq news agency, which is associated with the Islamic State group, said the terrorist organization had destroyed a gas plant in the desert outside the central city of Palmyra on Sunday.

Islamic State militants retreated from the ancient city two months ago but continue to operate in the surrounding area.

Syria's conflict, which started with largely peaceful protests against the government, descended into a sectarian war that has pulled in regional and global powers, killed at least 250,000 people and displaced half its pre-war 22 million population.

(Reporting by Suleiman Al-Khalidi; Editing by Andrew Heavens)