BEIRUT (AP) — Syrian opposition activists say government forces have shelled rebel-held villages in the country's northwest, inflicting casualties.

The Britain-based Syrian Observatory for Human Rights said Friday's shelling is the most serious violation of a truce reached by Turkey and Russia last month.

The Observatory said seven people, including three women and three children, were killed in the shelling of Umm Jalal and Rafa villages in Idlib province.

The area is part of a demilitarization zone that was agreed upon between Russia and Turkey to avert a government offensive on Idlib, the last major rebel stronghold in the country.

The Smart News, an opposition activist collective, reported casualties in Rafa without giving a breakdown.

The Russia-Turkey deal that went into effect on Oct. 15 has been violated on several occasions.