Beirut (CNN) -- Syria carried out an airstrike on a refugee camp in northern Lebanon Saturday, killing nine Syrians and wounding nine more, a Lebanese state-run news agency reported.
The strike centered on a Syrian refugee camp located near the Syrian border between the towns of Baalbeck and Arsal in the Bekaa Valley, the National News Agency said.
The Red Cross took the casualties to Universal Hospital in Baalbek.
Saturday's strike was not the first by the Syrian government, which has accused rebels of smuggling arms and supplies across the border.
On March 18, two Syrian jets fired three rockets that hit empty buildings near Arsal.
At the time, a U.S. State Department spokeswoman called the use of fighter jets to fire rockets into Lebanon a "significant escalation."
Also in March, the U.N. Security Council voiced "grave concern over repeated incidents of cross-border fire which caused death and injury among the Lebanese population, incursions, abductions and arms trafficking across the Lebanese-Syrian border, as well as other border violations." The declaration followed a briefing by officials on how the conflict in Syria has spilled into Lebanon.
More than 600,000 Syrians have fled to neighboring Lebanon, a country of about 4 million people, according to a U.N. estimate. But the Lebanese government puts the total at more than 1 million. Whatever the true figure, there is no dispute that the influx has destabilized the area and heightened tensions.
The attack comes as the Syrian conflict is mired in a third year of unrest, which started in March 2011 when President Bashar al-Assad cracked down on peaceful protesters.
Since then, it has evolved into a civil war that has killed more than 100,000 and transformed more than 1 million others into refugees, according to the Red Cross.
CNN's Nick Paton Walsh reported this story from Beirut, and Tom Watkins wrote it in Atlanta. CNN's Hamdi Alkhshali and Yousuf Basil contributed to this report