Nusra Front, also known as Al-Qaeda's affiliate in Syria, has amped up its presence in the city of Aleppo, the country's divided and former economic capital, according to activists' reports on Wednesday.
The Syrian Observatory for Human Rights reported that Nusra has established new positions in several districts of Aleppo after sending in a convoy of 200 vehicles carrying fighters.
The faction has arrived in rebel-held eastern Aleppo, according to the Britain-based Observatory who sources its information from a vast network of informants on the ground.
Nusra shared a video showing dozens of four-wheel-drive vehicles transporting fighters through Aleppo on Twitter.
"This show of force could signal that Nusra is preparing to take over command of future battles in Aleppo" against forces of the Syrian regime, the Observatory reported.
Rami Abdel-Rahman, the head of the monitoring group, said other rebel movements in the city were weakening. Of them, the Nour al-din al-Zinki Battalion of moderate Islamists is said to be losing funds and will soon be unable to feed its 4,000 fighters or repair its vehicles.
The Observatory added that Nusra's reinforcements arrived from Idlib province, a stronghold of the group in northwest Syria near the border with Turkey.
A security source claimed in January that pro-regime forces were planning to launch a major offensive to retake Aleppo province and cut off supply routes used by rebels in the provincial capital.
Much of Aleppo province is controlled by Nusra and its militant allies, or controlled by Daesh.
