Gunmen loyal to opposite sides in neighboring Syria's civil war battled on Wednesday in the streets of a northern Lebanese city where two days of clashes have killed at least six people and wounded more than 50, officials said. The Lebanese army fanned out in the city of Tripoli in an attempt to calm the fighting, with soldiers patrolling the streets in armored personnel carriers and manning checkpoints. The fighting comes at a time of deep uncertainty in Syria, with rebels fighting government troops near Assad's seat of power in Damascus. In Brussels, U.S. Secretary of State Hillary Rodham Clinton reiterated concerns that "an increasingly desperate Assad regime might turn to chemical weapons" or lose control of them to militant groups. She also said NATO's decision on Tuesday to send Patriot missiles to Turkey's southern border with Syria sends a message that Ankara is backed by its allies. The missiles are intended only for defensive purposes, she said. Turkey's foreign minister, Ahmet Davutoglu, was quoted Wednesday in the Turkish newspaper Sabah as saying that Syria has about 700 missiles, some of them long-range. "At this very moment we know where those missiles are, how they are being stored, whose hands they are in," he said. A Sunni gunman fires his weapon during clashes that erupted between pro and anti-Syrian regime gunmen in the northern port city of Tripoli, Lebanon, Wednesday, Dec. 5, 2012. Gunmen loyal to opposite sides in neighboring Syria's civil war battled in the streets of northern Lebanon at a time of deep uncertainty in Syria, with rebels closing in on President Bashar Assad's seat of power in Damascus. (AP Photo/Hussein Malla) Close U.N. Secretary-General Ban Ki-moon on Wednesday also urged Syria's regime against using its stockpile of chemical weapons, warning of "huge consequences" if Assad resorts to such weapons of mass destruction. Also Wednesday, U.S. officials said the Obama administration is preparing to designate a Syrian rebel group with alleged ties to al-Qaida as a foreign terrorist organization. The step seeks to isolate extremists within the Syrian opposition while the West tries to bolster those it supports. The largely symbolic move will freeze any assets that members of the group, Jabhat al-Nusra, have in U.S. jurisdictions and bar Americans from providing the group with material support, the officials said. The administration hopes the designation will complement its expected announcement to recognize the opposition's new leadership council as the sole legitimate representative of the Syrian people at an international conference in Morocco on Dec. 12. The officials spoke on condition of anonymity because they were not authorized to preview the designation publicly. The Syrian crisis has spilled over into Turkey, Israel and Jordan over the past 20 months, but Lebanon is particularly vulnerable to getting sucked into the conflict. Lebanon, a country plagued by decades of strife, has been on edge since the uprising in Syria began, and deadly clashes between pro- and anti-Assad Lebanese groups have erupted more than a dozen times.