Activists and local residents say intense clashes between a Western-backed rebel group and al-Qaida's Syrian affiliate have killed at least 20 fighters on the outskirts of the northern city of Aleppo.

The Britain-based Syrian Observatory for Human Rights says fighters from the al-Qaida-linked Nusra Front battled members of the mainstream Hazm Movement late Friday and early Saturday. It says Nusra fighters overran several Hazm bases near the town of Atarib.

An Aleppo-based activist who goes by the name Abu al-Hassan told The Associated Press that the two groups have had "numerous disagreements" in recent weeks.

The Observatory said that 29 Hazm fighters and six Nusra Front militants were killed in the clashes.