Damascus:The Al-Qaeda-linked Nusra Front and allied militant groups have captured three towns in the country's northern province of Aleppo, following battles with the Syrian army, a monitor group reported on Saturday. The Nusra and other groups have been engaged in intense battles with the army in Aleppo over the past four days as the terror groups unleashed wide-scale offensives against the government troops' positions, Xinhua news agency quoted the Syrian Observatory for Human Rights as saying. The Britain-based watchdog group said the rebels finally managed to capture the towns of Zaytan, Khalsa and Burneh. The four-day-long battles were coupled with intense airstrike by the Syrian air force against the positions of rebel groups south of Aleppo. The rebels' capture of the three towns have besieged the Syrian government forces in the town of Al-Hader in southern Aleppo. Observers believe if the army could not do anything to retake those towns, the government soldiers will come under heavy attack in Al-Hader. The battles in Aleppo have been raging on several fronts between various fighting groups. The army is busy fighting Nusra in southern Aleppo, while the US-backed Syrian Democratic Forces (SDF) are fighting the Islamic State group in the key city of Manbej in northern Aleppo, near the Turkish borders. The observatory, which relies on a network of activists on ground, said the rebels fired several mortar shells into government-controlled parts in Aleppo after midnight, the latest in a series of endless shelling in that city. It said over seven people were killed and 40 others wounded on Saturday by refreshed shelling on the district of Sheikh Maksud, a predominantly-Kurdish district controlled by the Kurdish People's Protection Units (YPG) in Aleppo. Sheikh Maksud has been under heavy shelling from the rebels since February, which led to the killing of 132 civilians and the injury of 900 others, the observatory added. Aleppo is a stage for intense battles due to its strategic importance and location near the Turkish borders.