The explosion occurred as officials sent the Lebanese army and riot police to secure the capital as demonstrators threw sticks and stones. The blast injured several military personnel and three civilians, the Kuwait News Agency said.
Tensions in Lebanon escalated as the opposition Free Patriotic Movement of former military commander Michel Aoun called for the ouster of Lebanese Prime Minister Fouad Siniora. The trade union General Labor Confederation called for a general strike Wednesday to demand higher pay, the Daily Star newspaper in Beirut said.
Aoun protested a move to elect former Lebanese military commander Michel Suleiman as the next president without amending electoral laws. Aoun, a Christian, said the current law was unfair to the Lebanese Christian community.
Former Lebanese President Amin Gemayel backed Aoun's sentiments, saying talks with various political parties had reached a dead end. Parliament plans to convene Tuesday elect a new president following 18 postponements. Lebanon has been without a president since Emile Lahoud stepped down in November.
"It is not likely that a president would be elected on May 13," Gemayel said.