The Islamic Jihad on Friday vowed a "harsh response" to the car bombing that killed Mahmoud Majzoub, the group's leader in southern Lebanon earlier Friday. Majzoub's brother was also killed in the blast, for which the Islamic Jihad blamed Israel. Israeli military officials said they had heard about Friday's incident through media reports, but have no additional information. Majzoub, a member of the group's policy-making Shura Council body and its leader in Sidon, 40 kilometers south of Beirut, was walking with his brother Nidal near the central square of this coastal city, when a parked car was detonated by remote control, security officials said. Mahmoud Majzoub survived the explosion but died during surgery. His brother Nidal was instantly killed, said the security officials, who spoke on condition of anonymity because they were not authorized to release the information. The explosion of a silver Mercedes parked at the roadside broke the windows of several nearby apartment buildings. Lebanese police and soldiers sealed off the area as dogs searched for additional bombs. "I rushed to the balcony after hearing the blast only to see black smoke billowing from a car," said Omran Kaddoura, a 16-year-old resident. After running down six flights of stairs to the street, he "found the two bloodied men lying on the ground in front of the car. Within minutes an ambulance picked them up." Earlier, before Mahmoud died, Islamic Jihad's representative in Lebanon, Abu Imad Rifai, blamed Israeli intelligence for the attack. "This morning the Israeli Mossad detonated an explosive charge ... This is the second time Mahmoud is targeted and I believe it comes in the framework of Israeli escalation against the Palestinian people, particularly Islamic Jihad," Rifai told The Associated Press. Mahmoud, 41, his wife and infant son were wounded in an explosion in 1998 in Sidon when their booby-trapped car detonated. Islamic Jihad blamed Israel for the blast that also injured a passer-by. Rifai confirmed that Nidal, 39, was a member of the group. Rifai rejected the possibility that other Palestinian or Lebanese groups were behind the attack. "No one has an interest in assassinating him except the Israeli Mossad."