Media reports say Islamist militants breached Syria’s largest city on November 29 and clashed with government forces for the first time since 2016.  

The advance on Aleppo reportedly followed a shock offensive launched by the militants on November 27, as thousands of fighters swept through villages and towns in Syria’s northwestern countryside.

Residents fled neighborhoods on the city’s edge because of missiles and gunfire, according to witnesses in Aleppo.

The UK-based Syrian Observatory for Human Rights (SOHR), which monitors the country’s unresolved civil war, said dozens of fighters from both sides were killed.

The attack injected new violence into a region experiencing dual wars in Gaza and Lebanon involving Israel, and other conflicts, including the Syrian civil war that began in 2011.

AFP news agency says the Syrian government has lost control of Aleppo for the first time since the country's civil war began in 2016. 

According to the BBC, the offensive has been led by the Islamist militant group Hayat Tahrir al-Sham (HTS), as well as allied factions backed by Turkiye.

Hayʼat Tahrir al-Sham (‘Organization for the Liberation of the Levant' or 'Levant Liberation Committee'), commonly referred to as Tahrir al-Sham, is a Sunni Islamist political and armed organization involved in the Syrian civil war.  It was formed on January 28, 2017 as a merger between Jaysh al-Ahrar (an Ahrar al-Sham faction), Jabhat Fateh al-Sham (JFS), Ansar al-Din Front, Jaysh al-Sunna, Liwa al-Haqq, and Nour al-Din al-Zenki Movement.  The unification process was held under the initiative of Abu Jaber Shaykh, an Islamist commander who had been the second Emir of Ahrar al-Sham.

CBS News reports that observers said the rebel forces were often met with little to no resistance by regime forces, but by Monday the pace of the surprise offensive appeared to have slowed, with Assad and his Russian backers ramping-up their response.

IRNA reported yesterday that Iranian and Russian presidents have discussed “recent terrorist activities in northern Syria, emphasizing the necessity of joint efforts to assist the Syrian government in countering terrorist groups.”

During a phone conversation on Monday evening, Iranian President Masoud Pezeshkian and his Russian counterpart Vladimir Putin reportedly reviewed the developments involving terrorist groups in northern Syria.

Both presidents described these movements as a serious threat to Syria's stability and regional security.

Pezeshkian highlighted that while the ceasefire in Lebanon had sparked hopes for regional calm, renewed terrorist activities in northern Syria, backed by the Zionist regime, have once again placed the region on high alert.

The Iranian president warned that the resurgence of terrorists in Syria threatens not only the country’s security and stability, but also poses a significant risk to the broader region.  

Commending Russia's pivotal role in maintaining regional peace and supporting Syria's territorial integrity, Pezeshkian reaffirmed Iran’s readiness to collaborate closely with Russia to address the crisis and support the Syrian government.

In response, Putin reportedly echoed Iran’s concerns, condemning terrorist activities in northern Syria and their impact on Syria's sovereignty and regional stability.  He emphasized that the root of the current unrest lies not with the terrorists alone, but with their external backers.

Putin reiterated Russia’s commitment to cooperating with Iran to aid Syria in confronting terrorist threats.

The Russian president further stated that Moscow would leverage all available diplomatic channels to contain the situation and curb the spread of terrorism.

He announced a proposal for an emergency meeting of the Astana Format later this week to address developments in Syria, alongside consultation with the UN Security Council on the matter.

Citing SOHR, Western media outlets report that Russia carried out "a series of air strikes in Syria on Sunday as rebels advanced after seizing Aleppo”. 

The BBC says warplanes also struck rural parts of Idlib and Hama “where the group leading the rebel offensive "has recently taken control”. 

Meanwhile, US, Germany, France and UK call for de-escalation in Syria. Issued on Sunday, a joint statement calls for the de-escalation of violence in Syria. 

Euronews reports that in their joint statement, the countries urged de-escalation for the “protection of civilians and infrastructure to prevent further displacement and disruption of humanitarian access”.

The United Nations Office for the Coordination of Humanitarian Affairs said over 14,000 people, including children, had been displaced by the violence in recent days.