(CBS NEWS) Fighter jets in support of Syrian President Assad’s regime struck targets near the town of Arsal, Lebanon, the U.S. State Department has confirmed.

The strikes, which were first reported by Lebanon’s state-run National News Agency, came just days after Damascus warned Beirut to stop militants from crossing the border to fight alongside the rebels.

“We can confirm what you are seeing in the press, that regime jets and helicopters did fire rockets into northern Lebanon,” State Department spokeswoman Victoria Nuland told reporters at her daily briefing. “This constitutes a significant escalation in the violations of Lebanese sovereignty that the Syrian regime has been guilty of. These kinds of violations of sovereignty are absolutely unacceptable.”

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