Syrian forces have fired into a refugee camp across the border with Turkey, killing two people.
The attack happened overnight in Kilis, just nine kilometres inside Turkish territory.
At least 15 other people were injured in the first incident of its kind since Turkey started to take Syrian refugees last summer.
Ankara said it has already protested to the Syrian charge d’affaires over the attack.
President Bashar Assad’s troops are supposed to pull out of towns and cities across Syria tomorrow under a deal by UN envoy Kofi Annan.
It is the first stage in a six-point plan for talks between the regime and its opponents.
Annan will visit the camps in Turkey later on Tuesday.
Some 25,000 refugees are now housed in makeshift tents on the three Turkish provinces bordering Syria.
Rebel forces say they will respect the plan’s Thursday deadline to end all violence.
But Syria says it cannot abide by any deal without written guarantees; a demand already rejected by the opposition.
The London-based Syrian Observatory for Human Rights said that 180 people died across Syria at the weekend.
The United Nations estimates more than 9,000 civilians have lost their lives since the start of the uprising against the Assad family’s four decade rule.