Fighting raged on Sunday near Aleppo international airport and nearby air bases as the battle for Syria's second city entered its second year, a monitoring group said.
"Fierce clashes broke out at dawn near Aleppo international airport and Nairab air base," said the Syrian Observatory for Human Rights, also reporting fighting in the Suleiman Halabi district of the city, once Syria's commercial hub.
The Britain-based watchdog also reported overnight clashes at Kwayris military airport.
The violence in Aleppo comes a year after a massive rebel advance into the provincial capital.
Stalemate has gripped the city ever since, dividing it into areas under and out of government control.
The pro-regime Al-Watan daily on Sunday lashed out at the Aleppo rebels, saying they "have not succeeded in securing their goal of taking control of Syria's commercial capital".
Over the past year, insurgents have fought hard to take Aleppo's airports, aiming to stop regime warplanes from bombing areas they control.
The city's international airport has been closed since January.
Tens of thousands of Aleppo residents have fled the fighting which has severely damaged one of the Middle East's richest cities in terms of culture and history.
Parts of the ancient souks in the heart of Aleppo were destroyed by fire last September, and the minaret of the famed and ancient Umayyad mosque has been blasted apart.
An archaeological treasure in Aleppo's UNESCO-listed Old City, the mosque was the focus of fighting for months and had already suffered extensive damage.
As with other attacks in the spiralling conflict, the government blamed the jihadist Al-Nusra Front, while rebels, the opposition and activists all blamed the army.
Elsewhere, the Observatory on Sunday reported a Republican Guard officer killed by rebels at a key flashpoint.
"Fighting in Adra on the northeastern outskirts of Damascus left an elite Republican Guard officer dead," Observatory director Rami Abdel Rahman told AFP.
Adra is an entry point to the capital's key Abbasiyeen Square, the target of several insurgent attacks in recent months.
State news agency SANA said the army "captured several terrorists from Al-Nusra Front, some of them foreign nationals", west of Adra.
Sunday's violence comes a day after at least 109 people were killed nationwide, said the Observatory which estimates a death toll of more than 100,000 people in the 28-month war.