Air strikes were carried out Sunday on a residential area of Al-Bab, a rebel rear base near Syria's second city of Aleppo as columns of smoke rose from the northern commercial hub.
Fighting in Aleppo was limited to a handful of neighbourhoods, opposition fighters said, although mortar blasts shook the battlefront district of Salaheddin and a warplane circled over the city.
"Clashes today are concentrated in the neighbourhoods of Salaheddin, Omriya and Izaa," a rebel fighter manning a checkpoint told AFP.
There had also been fighting near Aleppo's international airport and a military air base.
It was difficult to determine casualty figures in the ranks of the Free Syrian Army (FSA) as most doctors are only willing to give details on civilians, most of them hurt during shelling.
A hospital near the contested neighbourhoods of Salaheddin and Seif al-Dawla, which were quiet compared with previous days, received the corpses of three fighters early in the morning, a doctor said.
"Fighters bundled them up in sheets and took them away before we could write down their names," said Dr Jacques Beres, a Frenchman on his third humanitarian mission to Syria this year.
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There were at least six rebels wounded in Sunday's clashes, including a young man whose face was pierced by a bullet that entered from one cheek and exited from the other, said an AFP journalist who visited two hospitals.
Meanwhile, Al-Shifaa hospital, which mainly treats civilians, recorded the deaths of a man and a boy killed by shrapnel when an artillery round hit their home in Al-Muasalat neighbourhood.
A doctor who only identified himself as Osama said he had "received three people with severe head injuries" early in the morning.
Patients from the rebel ranks typically suffered severe bullet wounds to the neck and head and lighter injuries caused by shrapnel, he said, stressing that in 50 days of conflict he had "never treated a fighter hit by mortars or shelling."
Nurses at Al-Shifaa treated a one-year-old boy, Omar, who screamed in pain when disinfectant was applied to a gash on his forehead caused by shrapnel, the AFP journalist reported.
In nearby Al-Bab, a base for FSA fighters just 30 kilometres (18 miles) north of Aleppo, residents woke up to bombing which destroyed a car repair shop and another building but caused no casualties.
"The plane circled and circled and circled before it dropped the bomb," said Ahmed, a resident of the town which is periodically targeted. He pointed out fragments of vehicles protruding out of the debris.
Columns of smoke also rose over three patches of farmland along the road connecting the town of Al-Bab to Aleppo, according to AFP journalists who visited both cities.
And a MiG fighter jet overflew the eastern perimeter of Aleppo in the late afternoon.