Israeli armed forces swept through half a dozen Palestinian towns on Monday and arrested more Hamas officials, expanding a search for three teenagers into a crackdown on the Islamist group accused of abducting them.In al-Jalazoun refugee camp, near the de facto Palestinian capital of Ramallah, Palestinians threw rocks at Israeli troops and army gunfire killed a 20-year-old Palestinian and wounded another, hospital officials said.Israel says members of Hamas, which signed a unity deal with Palestinian President Mahmoud Abbas in April, kidnapped the three seminary students. They disappeared on Thursday after leaving a Jewish settlement in the occupied West Bank.Lieutenant-General Benny Gantz, chief of Israel's armed forces, said the military was preparing to expand its operation."We have a goal, and that is to find these three boys and bring them home, and to hit Hamas as hard as possible - and that is what we are going to do," Gantz said in broadcast comments, at a meeting with army officers."We are on our way toward a significant campaign. We will get our plans in order."Prime Minister Benjamin Netanyahu, who broke off peace talks with Abbas after the Palestinian reconciliation pact, held a rare telephone conversation with the Western-backed Palestinian leader on Monday.The prime minister's office said in a statement that Netanyahu told Abbas he expected him to help in efforts to find Gil-Ad Shaer and U.S.-Israeli national Naftali Frankel, both 16, and Eyal Yifrah, 19.