The Bab al-Hawa crossing between Syria and Turkey was hit by a car bomb Tuesday, which reportedly killed seven people, according to Turkish media.
Reports said at least 20 others were wounded in the explosion, near a roadblock controlled by Syrian rebels.
"The objective is to destabilize security at the crossing. The casualties are all civilians, from the people queuing to cross," said Omar Aref, an activist.
The Syrian military on Tuesday accused Turkey of trying to escalate tensions by shooting down a Syrian helicopter that had "mistakenly" flown into Turkish airspace on Monday.
Syria claimed the helicopter, which had strayed more than a mile into Turkey's airspace, was on a mission to monitor rebels crossing the border.
Turkish Deputy Prime Minister Bulent Arinc said on Monday that the helicopter was shot down after ignoring repeated warnings to leave Turkish airspace.
The Syrian military put out this statement late on Monday:
"The hasty response from the Turkish side, especially as the aircraft was on its way back and was not charged with any combat missions, is proof of the true intentions of Erdogan's government toward Syria to increase tensions and escalate the situation on the border between the two countries."
"Nobody will dare to violate Turkey’s borders again," Turkish Foreign Minister Ahmet Davutoglu reportedly said. "The necessary measures have been taken."
Turkey, which once enjoyed a close relationship with Syria, now plays host to 500,000 Syrian refugees, and Prime Minister Recep Tayyip Erdogan has called for Syrian President Bashar al-Assad's ouster.
The border between Syria and Turkey, once thought to be a "crossroads for traders, business people and tourists — now teems with refugees, smugglers and insurgents," according to TIME.
Since June 2012, when Syrian forces shot down a Turkish fighter jet, approximately 75 people have died along the border between the two nations, according to the International Crisis Group.
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