A couple and their four children, the youngest just six months old, were killed Sunday in Syrian army air raids in the northern province of Aleppo, a monitoring group said.

"An entire family was killed in air raids in Tal Rifaat in the north of Aleppo province," the Syrian Observatory for Human Rights said.

"The parents and their children, aged 10, six, two and six months, were all killed," in the strikes targeting the rebel-held town.

"(President) Bashar al-Assad says he wants to kill terrorists. Is a six-month-old baby a terrorist?" asked Observatory director Rami Abdel Rahman.

More than 2,000 civilians have been killed since January in a regime aerial campaign targeting Aleppo province, most of which is under rebel control.

Aleppo city, the country's pre-war commercial capital, has been divided between rebel and regime control since shortly after fighting began there in mid-2012.

The campaign has included frequent attacks with explosives-packed barrel bombs dropped from helicopters, a tactic rights groups condemn as indiscriminate.