While Russia had carefully worked out a deal with Syria and Turkey on the question of dividing the Aleppo Province in the near-term, Turkey’s rebel allies appear not to have been in on the deal, or at least not so much as everyone else would have liked, and overnight carried out attacks on Syrian troops south of al-Bab.

Syria’s military had recently made gains against ISIS in villages south of al-Bab, an offensive aimed at securing the water supply for the city of Aleppo. The gains also complicate the Turkish military offensive, but appear to have been in-line with the deal Russia brokered.

A statement from a Turkey-backed Free Syrian Army force accused the government of trying to advance too close to al-Bab, and claimed to have killed 22 soldiers in the fighting. Syrian military reports said the rebels had attacked them with artillery, referring to the faction as “terrorist groups that belong to Turkey.” They did not, however, confirm the casualty figures.

Since their invasion of northern Syria in August, Turkey has been eager to use rebel factions as allies in fighting against ISIS, but the groups are rebels first and foremost, and eager as they were to accept a big chunk of territory that the Turkish invasion netted them, they were always going to shift back to fighting the government at some point.