( CNN ) -- Israel came under attack Sunday on two fronts , according to the Israeli military . In an incident near the Israeli-Syrian border , a 15-year-old Israeli civilian was killed and two others were injured , the Israeli military said . `` Today 's event on the Syria border intentionally targeted Israelis . The explosion is the most serious attack against Israel in recent months , '' the Israel Defense Forces tweeted from its official account on Sunday morning . `` This is not a case of errant fire , but of an intentional attack , '' IDF spokesman Lt. Col. Peter Lerner said . It was unclear whether the incident was connected to the Syrian civil war , but violence from that conflict has spilled over into northeastern Israel before . In response , Israel fired on nine Syrian army positions , including Syrian military headquarters and launching positions , the IDF reported . The IDF reported direct hits . On the southwestern side of the country , two rockets hit the Sha'ar Hanegev Regional Council , which borders Gaza , and an arrest was made of a `` terrorist carrying a hand grenade '' who the IDF believes `` infiltrated Israel through the Gaza security fence , '' according to the IDF 's blog . In response , the IDF `` targeted four terror activity sites in Gaza , '' the blog said . Earlier Sunday , the Israeli military shot and killed two Palestinian men in the West Bank , medical officials said . Mohammad Mahmmoud Ismail , 30 , was killed during a raid in Ramallah . The Israeli military said it was investigating . In addition , Ahmad Saeed Khaled , 27 , was killed during a raid at a refugee camp in Nablus , a Palestinian doctor said . Khaled , a psychiatric patient , was going to morning prayers when he was shot in the legs , chest , and head , according to Dr. Ghassan Hamdan of the Palestinian medical relief society . The Israeli military said it shot a man who approached in a threatening manner in Nablus . `` The force called on the suspect to stop and after he failed to comply , they fired warning shots in the air . The troops then fired toward the suspect , after he did not cease to advance . Initial inquiry suggests that the suspect was mentally unstable , '' the IDF said . An investigation is under way . The violence comes amid an Israeli operation in response to the kidnapping of three Israeli teenagers , one of whom is reported to be a U.S. citizen . The Palestinian medical sources say five people have died since the onset of the operation : four from Israeli military fire , and a fifth from a heart attack during a raid on his West Bank home . An additional 463 Palestinians , including children , had been arrested or detained as of Sunday morning , according to the Palestinian Prisoners Society . READ MORE : U.S. church dumps Israeli investments in protest . Kareem Khadder wrote and reported on this story from Jerusalem and Brian Walker and Mark Morgenstein wrote this story in Atlanta .
Attack from Syria on Israeli teen , Israel fires back , IDF says . 2 people were killed in the West Bank , officials said . More rockets are fired into Israel from Gaza . Violence continues amid operation in West Bank after killing of 3 Israeli ##s .