BEIRUT — Syrian government forces launched a counteroffensive Saturday under the cover of airstrikes, trying to regain control of areas they had lost to insurgents the day before in the northern city of Aleppo, activists and state media said.

Meanwhile, insurgents launched a fresh offensive on the city, a day after embarking on a broad ground attack aimed at breaking a weekslong government siege on the eastern rebel-held neighborhoods of Syria’s largest city.

The insurgents captured much of the western neighborhood where much of Saturday’s fighting was concentrated, according to the Syrian army and the Britain-based Syrian Observatory for Human Rights.

The Observatory said the new offensive by Syrian troops and their allies went under the cover of Russian and Syrian airstrikes but government forces did not succeed in regaining control of areas they lost. The group said the fighting and airstrikes are mostly on Aleppo’s western and southern edges.

The Syrian army command said troops and their allies are pounding insurgent positions with artillery and rockets, adding that “all kinds of weapons” are being used in the fighting in the neighborhood.

The Aleppo Media Center, an activist collective, reported airstrikes and shelling of areas near Aleppo. The AMC and another activist collective, the Local Coordination Committees, said rebels entered the village of Minian west of Aleppo on Saturday after intense fighting with government forces.

Later Saturday, the rebels said they launched an attack on the Zahraa neighborhood in western Aleppo to try to capture it from government forces. The attack began with a massive explosion that struck government positions on the front line, said Yasser al-Yousef of the Nour el-Din el-Zinki group, a main faction in Aleppo.

The Syrian army said troops were repelling the attack on Zahraa. It said the offensive began when the insurgents detonated a vehicle and shelled the area.

The Observatory said the fighting was continuing intensely after sunset, saying that government forces detonated explosives and bombs they planted earlier in the area in an attempt to repel the offensive on Zahraa.

Syrian state media said rebels shelled government-held western neighborhoods of Aleppo on Saturday morning, wounding at least 10 people, including a young girl.

Rebel shelling of Aleppo on Friday killed 15 and wounded more than 100.

On Friday, insurgents including members of Fatah al-Sham and the ultraconservative Ajnad al-Sham and Ahrar al-Sham militias took advantage of cloudy and rainy weather to attack government positions.

The Observatory said that since Friday some 30 troops and members of Lebanon’s Hezbollah group were killed in the Aleppo fighting.

East Aleppo has been subjected to a ferocious campaign of aerial attacks by Russian and Syrian government warplanes.