After allegedly being hit by cross-border mortar strikes from Syria, Turkey has responded by shelling a number of key sites in Syria.
It's a tense situation, and despite claims from the US ("nothing to suggest it's going to become a broader conflict," one US official told CNN), many are worried about the prospect of a war.
Turks in particular seem keen to avoid conflict. Right now the top trending topic worldwide is #Savaşahayır, which roughly means "no to war" in Turkish (although not everyone is using it seriously).
Here's a selection of the top tweets in English at the time of writing:
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