In the wake of rebels gaining control of Aleppo, Iranian-backed Iraqi militias crossed into Syria overnight to help the government fight these rebels. Tehran pledged to aid the Damascus government.
Avoiding the official border crossing, at least 300 fighters, from the Badr and Nujabaa groups, crossed late on Sunday using the dirt road.
According to a senior Syrian military source, fresh reinforcements are being sent to aid the comrades on the front lines in the north.
Iran's constellation of allied regional militia groups has long been integral to the success of pro-government forces in subduing rebels who rose up against President Bashar al-Assad in 2011, and they have long maintained bases in Syria.
Iranian Foreign Minister Abbas Araqchi said on Monday that Syria's military was capable of confronting the rebels but referring to the regional militia groups Tehran backs, he added that "resistance groups will help and Iran will provide any support needed".
Syrian government and Russian warplanes intensified attacks on Monday in areas held by rebels in the northwest.
In a big blow to the Bashar-al-Assad regime, rebels took control of Aleppo last week reigniting a conflict that had appeared frozen for years after civil war front lines stabilised in 2020.
Russia retains an air base in northern Syria, though it has been engaged in war with Ukraine.
Syria's conflict erupted in a rebellion against Assad's rule in 2011 and the rebels held much of Aleppo from 2012 until 2016, when government forces retook it with help from Russia and Iran-backed militia in a major turning point of the war.
The rebels include mainstream groups backed by Turkey, as well as the Islamist Hayat Tahrir al-Sham which was formerly affiliated with al-Qaeda.
Turkey also has a military presence in a strip of Syrian territory along its border.
Russia's support turned the military balance decisively in Assad's favour continues to support the Syrian president and is analysing the situation on the ground, Kremlin spokesperson Dmitry Peskov said.