The Syrian Observatory for Human Rights said on Friday that rebels seized a village from government forces near Aleppo overnight.
The rebels are gaining important ground near the Syrian city where the US and Russia are trying to de-escalate the war.
The Syrian Observatory for Human Rights said that 73 people had been killed in the battle for Khan Touman, in a location near the Damascus-Aleppo highway.
However, Syrian army source denied Khan Touman had fallen.
The attack was launched by an alliance of Islamist insurgents known as Jaish al-Fatah, including the al Qaeda-linked Nusra Front, which has rejected diplomatic efforts to halt the war and promote peace talks.
The US and Russia this week brokered a ceasefire in the city of Aleppo itself, where some 300 people have been killed in the last two weeks in government- and rebel-held areas as a result of air strikes and shelling.
“Throughout the night the battles were very intense,” said Abu al-Baraa al-Hamawi, a fighter from the Ajnad al-Sham group, one of the factions taking part in the attack.
The Observatory said 43 of the dead were rebels and 30 were government forces.
Groups fighting under the banner of the Free Syrian Army, which have mostly supported diplomatic efforts in Syria, were not taking part in the attack, a fighter from one Aleppo-based FSA group said.