The Syrian military on Sunday sent reinforcements to halt the advance of jihadi insurgents in Hama province after the rebels seized most of the city of Aleppo and some nearby towns in a surprise offensive that is posing a massive challenge for Syria's autocratic leader, Bashar Assad.

The new rebel assault, led by Islamist group Hayat Tahrir al-Sham (HTS), is a major escalation in Syria's long-running civil war, which has seen relatively low-level violence since Assad regained control of two-thirds of the country several years ago with the help of allies Russia and Iran.

Russia has meanwhile continued with airstrikes on rebel positions, targeting towns and villages they hold in the northwestern province of Idlib and the central province of Hama, Britain-based opposition war monitor the Syrian Observatory for Human Rights said.

In five days of clashes and airstrikes the death toll "has reached 412," the Observatory reported. The figure including 214 rebels from Hayat Tahrir al-Sham and allied factions that launched the offensive, 137 pro-government forces and 61 civilians.

Government pushback

The Observatory, which gets its information from a network of eyewitnesses within Syria, said the reinforcements had formed a "strong defensive line" in the countryside in the north of Hama.

According to Syrian state news agency SANA and the Observatory, the army succeeded in pushing back insurgents in the region overnight.   

Syrian state television has claimed that government forces have killed nearly 1,000 insurgents over the past three days, though it gave no evidence for its figure.  

Four civilians were wounded and 54 others injured in government airstrikes overnight on Idlib city, a rebel-held stronghold near Hama province that is 65 kilometers (40 miles) southeast of Aleppo, according to the Syrian Civil Defense, also known as the White Helmets, which operates in opposition-held areas.

Rebels claim full control over Aleppo

With Aleppo largely in the hands of the insurgents, rebel commander Hassan Abdulghani has claimed the seizure of Sheikh Najjar, also known as the Aleppo Industrial City, northeast of the city, Aleppo's military academy and the field artillery college to the southwest.

The Observatory has said that the rebels now control almost all of Aleppo, Syria's second city, except for some Kurdish-ruled neighborhoods on the northwestern fringes.

"For the first time since the conflict started in 2012, Aleppo city is out of control of Syrian regime forces," Rami Abdel Rahman, the Observatory head, told AFP and dpa news agencies, although the claim cannot yet be independently verified.

Aleppo was secured by government forces, with the help of Russian airstrikes, in 2016 in a battle that was seen as a turning point in Syria's civil war.

Assad under pressure

President Assad said in comments released on Saturday evening that Syria would continue to "defend its stability and territorial integrity against terrorists and their supporters."

He added that Syria was able to defeat them no matter how much their attacks intensify.

However, the rebel offensive comes at a time when his allies — Iran and groups it backs and Russia — are focusing their efforts on other conflicts elsewhere, notably in Lebanon and Ukraine.

Nonetheless, Iranian Foreign Minister Abbas Araghchi, who traveled to the Syrian capital, Damascus, on Sunday, told reporters the situation was "difficult," but he added he was confident Assad's government would confront rebels as it has in the past. He also said Tehran would "firmly support the Syrian government and army," the IRNA state news agency reported.

Meanwhile, Turkish Foreign Minister Hakan Fidan discussed the shock rebel offensive in Syria with US Secretary of State Antony Blinken, saying Turkey would support moves "to reduce tension" in Syria.

He also called for progress in the political process between the Syrian government and the opposition to restore peace and added that Ankara would "never allow terrorist activities against Turkey nor against Syrian civilians."

The Observatory reported "armed clashes" between Kurdish YPG forces, which Turkey considers an offshoot of the Kurdistan Workers' Party (PKK), and pro-Ankara factions north of Aleppo city.

World eyes developments in Syria

Israeli Prime Minister Benjamin Netanyahu said his country is closely watching developments in Syria. "We are determined to defend the vital interests of Israel and to maintain the achievements of war," Netanyahu said.

Germany's Foreign Ministry said all parties in Syria must adhere to international humanitarian law following the resurgence of fighting. The ministry said the civilian population and infrastructure must be protected.

Meanwhile, UN special envoy for Syria Geir Pedersen said a lack of commitment to a peace solution in Syria has led to a renewed escalation of violence in the country's long-running civil war.

 "The latest developments pose severe risks to civilians and have serious implications for regional and international peace and security," he warned, urging the Syrian conflict parties and involved states to engage in negotiations.

tj/wmr (dpa, AFP, Reuters)