ISTANBUL 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."
Lebanon has been on edge since the uprising against Assad began in March 2011. Gunmen on opposing sides of Syrian civil war have frequently clashed in Lebanon, raising concerns of a spillover.
Assad's ally, the militant Hezbollah group, is Lebanon's strongest political and military movement and has been accused by Syria's overwhelmingly Sunni rebels of assisting Assad in his military crackdown. Assad belongs to a small branch of Shiite Islam.
Hezbollah denies any of its members are fighting alongside Assad but says several of its fighters have been killed while defending themselves against Sunni gunmen in areas along the border.
Syria's conflict began with political protests in mid-March, 2011, and has since become a civil war, with hundreds of rebel groups fighting Assad's forces. The U.N. says more than 70,000 people have been killed and millions have been pushed from their homes by the violence.
In addition to the strikes inside Lebanon, the Syrian capital Damascus saw heavy fighting on Monday.
At least three mortar shells struck central Damascus, the seat of President Bashar Assad's power. The pro-government's Al-Ikhbariya TV said one of the shells fell in Muhajireen district near Tishreen Palace, one of three palaces that Assad uses in the capital.
Activists also reported that mortar shells struck near state security agencies in al-Barakmeh district and close to the Higher Education Ministry in Mazzeh district.
At least 26 people died in the fighting in Damascus and its suburbs, according to the Britain-based Syrian Observatory for Human Rights.
Meanwhile, the leader of the main Syrian rebel force on Monday threw his weight behind the formation of an interim government to administer rebel-held areas as heavy fighting broke out in the Syrian capital and several suburbs.
In Istanbul, Gen. Salim Idris told reporters that fighters affiliated with his Free Syrian Army, the main rebel group, will work under the umbrella of an interim government and protect its members.
"We recognize the coalition as our political umbrella and we hope this government can be formed unanimously and that this government will exercise its powers in all of Syria," said Idris, the chief of staff of the FSA. "We consider it the only legal government in the country."