BEIRUT — Syrian rebels and insurgents said on Friday they are edging closer to breaking the government force’s siege of the opposition-held part of Aleppo, taking parts of the city’s military college close to a strategic siege area.

The announcement from two ultraconservative factions, including al-Qaida’s branch in Syria which is now known as the Levant Conquest Front, came on social media, saying they had pushed into the college, where artillery men trained in peace-time. The facility is located about 1 mile from the besieged opposition areas.

The Britain-based Syrian Observatory for Human Rights monitoring group confirmed that a part of the facility was captured. The activist group said fierce clashes had erupted around the college, with casualties on both sides.

The media office of Hezbollah, the Lebanese Shiite militant group fighting alongside Syrian President Bashar Assad’s forces, denied reports of a rebel advance.

The rebels on Friday also shelled a nearby, government-controlled neighborhood of Aleppo, killing at least three civilians, according to the Observatory. Syrian state media said five civilians, including three children, were killed.

The U.N. estimates that between 250,000 and 300,000 residents have been trapped in the besieged, eastern part of Aleppo since pro-government forces cut the last supply route in July.