The Britain-based Syrian Observatory for Human Rights said the dead, who included at least one child, were killed in air strikes on the village of Jalbara.
"Eight civilians were killed in missile strikes on a chicken farm where they were living," said Birusk Hasakeh, a spokesman for the Kurdish People's Protection Units (YPG) in Afrin, blaming Turkish warplanes.
In pictures sent by Hasakeh to AFP, Kurdish Red Crescent rescuers could be seen retrieving bloodied bodies from a collapsed concrete structure and laying them on orange stretchers.
It was the second day of "Operation Olive Branch," an offensive by Turkish forces and their Syrian rebel allies against the YPG-held Afrin region.
On Saturday, Hasakeh told AFP that Turkish bombardment had killed 10 people, including seven civilians.
Turkish Foreign Minister Mevlut Cavusoglu said Sunday that claims of civilian casualties from the offensive were untrue.
"As always, the PYD/YPG terrorists continue to deceive the world with nonsense propaganda and baseless lies by showing neutralised terrorists as civilians," he wrote on Twitter.
He was referring to the Kurdish Democratic Union Party and its armed wing, the YPG, fighting in Syria.
"They use civilians as human shields. Our target is neither our Kurdish brothers nor Syrians. We are only after terrorists."
And the Turkish army says it is doing everything possible to prevent civilian casualties.
"In the planning and execution of the operation only terrorists and their shelters, positions and weapons are being targeted," the army has said.
Turkish army tanks gather close to the Syrian border at Hassa, in Hatay province
Turkish air raids killed eight civilians on Sunday in the northern Syrian enclave of Afrin, according to a war monitor and a spokesman for the Kurdish forces that control the area.
