In the latest example of how Syria's civil war is spilling into neighboring Lebanon, a car bomb tore through a Shiite neighborhood in South Beirut Tuesday morning, leaving four people dead and 35 injured.“Body parts apparently belonging to a suicide bomber were at the scene,” Lebanon's National News Agency reported.Responsibility for the blast, which rocked the Hezbollah stronghold of Haret Hreik just after 11 a.m., was claimed by Al Nusra Front in Lebanon. It is the second blast to rattle the town of Haret Hreik this month. Al Nusra posted a statement on their Twitter account: “With the help of God almighty we have responded to the massacres carried out by the party of Iran [Hezbollah] … with a martyrdom operation in their backyard in the southern [Beirut] suburbs."The Syrian rebel group was formed in January 2012, and has been designated as a terrorist organization by the United Nations.Tensions are high among Lebanon's Sunnis and Shias as the violence continues to extend from neighboring Syria.