Syrian authorities have beefed up security measures in Damascus as rebels fighting to topple President Bashar Assad urged supporters to mark the second anniversary of the country's uprising by stepping up attacks against the regime. The revolt against Mr Assad's authoritarian rule began in March 2011 with protests in the southern city of Daraa, after troops arrested teenagers who scrawled anti-regime graffiti on a wall. It has since morphed into a civil war with an estimated 70,000 people killed, according to the U.N. Today, some rebels called for stepped-up attacks to mark the anniversary. The banned Islamist Muslim Brotherhood group urged supporters for a "week of action" on the occasion but didn't specify what it would do. A Damascus-based activist who identified himself as Abu Qais said troops increased patrols and security searches in the country's capital. Meanwhile, in neighbouring Lebanon, gunmen set fire to three fuel tankers with Syrian licence plates to prevent them from crossing into Syria, the state-run National News Agency said. Protesters have in the past closed roads to keep tankers from crossing into Syria, where there are severe petrol and diesel shortages. They claim diesel exported to Syria is being used by regime tanks. Many among Lebanon's Sunni Muslims have backed Syria's mainly Sunni rebel forces, in which radical Islamists have become increasingly active. Lebanese Shiite Muslims, including the militant Hezbollah group, have leaned toward Mr Assad, whose tiny Alawite sect is an offshoot of Shiite Islam. Separately, the Syrian Foreign Ministry complained in a letter sent to the Lebanese government that armed groups have tried to infiltrate Syria from Lebanon repeatedly in the past 36 hours, triggering clashes with border guards. Damascus said Syrian troops have exercised "utmost self-restraint" until now but warned that "this would not continue endlessly." Also today, at least eight Syrians were killed and 29 were injured when the bus they were travelling in from Syria overturned in the mountains in central Lebanon, officials said. The bus was headed to the Lebanese capital, Beirut, when the accident occurred in the Kahhaleh region. George Kettaneh, operations director for the Lebanese Red Cross, said the casualties included women and children. It was not immediately known whether the Syrians where refugees fleeing the violence at home. | 
