Al-Qaeda's affiliate in Syria, Al-Nusra Front, has boosted its presence in the country's divided former economic capital of Aleppo, AFP reports.
The Syrian Observatory for Human Rights said Al-Nusra has erected new positions in several districts of the northern city after having sent in a convoy of 200 vehicles loaded with fighters.
The group has deployed in rebel-held eastern Aleppo, said the Britain-based Observatory which relies on a vast network of sources on the ground for its information.
Al-Nusra itself posted on Twitter a video of dozens of four-wheel-drive vehicles transporting gunmen through Aleppo.
"This show of force could signal that Al-Nusra is preparing to take over command of future battles in Aleppo" against government forces, the Observatory said.
The monitoring group's head, Rami Abdel Rahman, said other rebel movements in the city were weakening, among them the Nureddin Zinki group of moderate Islamists that was running out of funds to repair its vehicles or feed its 4,000 fighters.