BEIRUT — Backed by warplanes, Syrian government troops pushed Thursday into the central districts of the city of Homs in an effort to oust rebels from the country's third largest urban center, activists said. The regime pounded rebel-held districts with artillery and carried at least one airstrike on a residential neighborhood, killing seven people, four of them children, said the Britain-based Syrian Observatory for Human Rights. President Bashar Al-Assad's troops regained control of the Wadi Sayeh district in the center of Homs by early Thursday morning, the observatory said. The neighborhood is strategically important for the government as its forces try to dislodge opposition fighters from several central districts that have been under rebel control for more than a year. In the northern city of Aleppo, rebels overran the headquarters of Assad's anti-terrorism forces, according to the Aleppo Media Center activists group. The building's capture was the latest in a string of rebel victories in Aleppo as opposition fighters try to expand their hold within the city, Syria's largest. The building is located near the central prison where many of Assad's opponents, activists and their family members are believed to be held. Rebel fighters have for weeks battled government troops in the area in an attempt to storm the facility and free the prisoners. Both Homs and Aleppo, along with the capital of Damascus, have been key battlegrounds in the country's conflict, which is now in its third year and has claimed more than 70,000 lives. The observatory, which relies on a network of activists on the ground, said regime jets also hit the northern city of Raqqa, killing eight people there Thursday. In early March, Raqqa became the first urban center to fall entirely under rebel control. In recent weeks, Assad forces have been on a counter offensive to reverse rebel gains in and around Aleppo, where the opposition controls whole neighborhoods and large swaths of land around the city. The army has also conducted massive sweeps through opposition strongholds around Damascus to oust rebels from their enclaves, from where they are increasingly threatening the capital, the seat of Assad power. Regaining full control of Homs would be a psychological blow to the opposition, which holds the city as a symbol of Syria's uprising, inspired by other Arab Spring revolts against authoritarian rulers around the Middle East. Homs was the scene of massive street protests against the regime in the first months of the uprising that began in March 2011. Since then, it has seen some of the worst urban warfare in the country's civil war. Also Thursday, Assad's warplanes hit several targets in Damascus province, including rebel positions in neighborhoods around the capital, as well as targets in the southern city of Daraa, the observatory said. Opposition activists also reported fierce clashes between Assad's troops and rebels near Aleppo's international airport. Aleppo, Syria's main commercial hub, has been carved up into opposition- and government-held areas since the rebels launched an offensive there last summer, capturing several districts and villages and towns around the city, which is near the border with Turkey. — AP