(CBS News) ISTANBUL- For a fourth straight day, Syria and Turkey traded fire Saturday, it's the latest sign Syria's civil war is now expanding into a threat to regional security.
Syria's civil war is spilling over its borders. On Saturday, the Turkish village of Guvecci was hit by two mortar shells.
Nobody was hurt and it's thought the shells were lobbed into Turkey by mistake, during fighting between Syrian rebels and regime forces.
But the Turkish military returned fire -- for the fourth day in a row.
Turkey has openly sided with the rebels in Syria's conflict, though so far it hasn't intervened directly.
Now some fear that border skirmishes between the two countries could escalate into a regional war.
On Wednesday, a mortar bomb fired from Syria killed five civilians in a Turkish border town, including a mother and her three children.
In response, the Turkish Parliament voted to approve the use of force against Syria if it's deemed necessary.
On Saturday, Turkish Deputy Prime Minister described that decision as a warning. "We have to protect our sovereignty, our security and the lives of our people," he said.
In the Syrian capital of Damascus, President Bashar al-Assad made a rare public appearance, laying a wreath to mark the anniversary of the 1973 war against Israel.
President Assad's regime is fighting for its survival, and it's unlikely that he wants to antagonize a powerful neighbor like Turkey.
But the bloody chaos that's already cost thousands of lives inside Syria now threatens to entangle other countries -- even if they don't really want to fight.