"I strongly condemn yesterday's shelling by Syrian forces of the Turkish border town of Akcakale, which killed five and injured many more," EU foreign affairs chief Catherine Ashton said in a statement, adding: "I call for restraint from all sides."
Also, British Foreign Secretary William Hague said the Syrian government should make sure that "there is no repetition whatever of any incident of this kind so that such tensions on border regions with Turkey or with other neighbouring countries can be avoided."
Turkey's military response to a Syrian mortar attack that killed Turkish citizens was understandable, but an escalation of the situation should be avoided, Hague told Reuters.
"The Turkish response is understandable, an outrageous act has taken place, Turkish citizens have been killed inside Turkey by forces from another country," Hague said. "So we express our strong solidarity with Turkey but we don't want to see a continuing escalation of this incident."