Syrian rebels maintained control of all four border crossings with Iraq and two with Turkey Friday as regime forces intensified their bombardment of Damascus. The rebels claimed for the first time they captured a pocket of Damascus after intense street fighting that drove thousands of residents from the city. Iraqi security officials backed up rebel claims they had seized an entire swathe of the country\'s frontier with Iraq. One video posted online showed rebel Free Syrian Army fighters defacing pictures of Syrian President Bashar Assad and his father -- and predecessor as president -- Hafez Assad, as the rebels overran several border crossings. One of the two crossings to Turkey captured by opposition fighters is at Bab al-Hawa, gateway to northwestern Syria\'s Idlib province, opposition leaders said and video posted online indicated. \"Idlib province will be Syria\'s Benghazi,\" an opposition activist told the British newspaper The Guardian -- referring to Libya\'s second city, the temporary capital of the Libyan rebel National Transitional Council during its successful routing of Libyan leader Moammar Gadhafi last year. As rebel forces claimed victories at the borders, troops loyal to the Assad regime intensified their bombardment of Damascus Friday, using attack helicopters and army tanks to attack rebel fighters still working predominately with small-caliber weapons. The Syrian military said its determination to \"clear the homeland of the armed terrorist groups\" -- the term it uses for insurgents seeking Assad\'s ouster -- had been fortified by the rebel bombing Wednesday that killed three top Syrian security chiefs. Witnesses reported seeing regime artillery, high-arcing ballistic trajectories and indirect-fire mortar attacks on several neighborhoods. The fighting spread to some of Damascus\' most exclusive neighborhoods. Army snipers spread across rooftops in Damascus\' Mezzeh neighborhood Thursday, the opposition Syrian Observatory for Human Rights said. Mezzeh -- one of Damascus\' most modern and expensive areas -- is a major embassy neighborhood. Fighting Thursday left 155 civilians and 93 regime soldiers killed throughout Syria, including about 60 civilians in and around Damascus, the Syrian Observatory said. Syrian state media said government soldiers killed at least 40 opposition fighters in Damascus and seized weapons and ammunition. Panicked residents fled the growing chaos, with an estimated 20,000 fleeing 25 miles to the closest crossing into neighboring Lebanon -- already home to nearly 30,000 Syrian refugees -- a Lebanese border official told The Wall Street Journal. The Lebanese minister of social affairs said 4,500 cars crossed into the country at the border crossing on the highway from Damascus. Israel put its military on alert to stop refugees crossing into its territory. Iraqi residents of Damascus fled the city in the other direction to the Iraqi border. More than 1,000 crossed into Iraq, but many others were unable to cross the rebel-controlled border due to heavy clashes that led Iraqi authorities to tighten border security, a top Iraqi official said. Baghdad said in a statement on state TV Thursday night it would send airplanes to Damascus to bring Iraqis -- many who fled the war in Iraq -- back home. The rebel advances and the Damascus fighting and exodus came as Russia and China vetoed a U.N. Security Council resolution that would have threatened sanctions against the Assad regime. U.S. Ambassador to the United Nations Susan Rice said, \"The council has failed utterly.\" The White House condemned the vetoes as \"highly regrettable.\" Syrian state media called the Chinese and Russian vetoes a \"double victory.\" It was the third time the two countries vetoed a resolution intended to pressure Assad to agree to a political transition from power.