JERUSALEM, May 18 (JTA) — Within hours after the polls closed, Israel’s newly elected premier got a taste of one of the challenges that will be confronting him. Prime Minister-elect Ehud Barak was celebrating his election victory late Monday night when Hezbollah gunmen in Lebanon fired Katyusha rockets at northern Israel. Barak told his backers that he wanted to send a “strong hand” of support to those Israeli citizens in northern communities who were spending the night in shelters. He also repeated a campaign promise to withdraw Israeli troops from southern Lebanon within a year. Barak has promised to re-open negotiations with Syria, the leading power broker in Lebanon, in an effort to bring peace to Israel’s last remaining war zone. By Tuesday afternoon, Israeli officials allowed residents of the northern town of Kiryat Shmona to leave the bomb shelters. Hezbollah gunmen, who fired dozens of the rockets, said they were retaliating for the deaths of two Lebanese civilians in earlier Israeli shelling. Four Israelis were lightly injured by the Katyusha assault, and one house sustained a direct hit. The rockets, which fell in the western and northern Galilee, caused an estimated $100 million in damage, Israeli officials said. The army denounced the attack, calling it a violation of a 1996 understanding against targeting civilians on either side of the Israeli-Lebanese border.